KR20130069157A - Light emitting device - Google Patents

Abstract

The present invention relates to a light emitting device capable of improving internal quantum efficiency, the first conductive semiconductor layer; An intermediate layer formed on the first conductivity type semiconductor layer and including at least one pair layer; An active layer formed on the intermediate layer in a multiple quantum well structure (MQW); And it provides a light emitting device comprising a second conductivity type semiconductor layer formed on the active layer. Here, the pair layer is formed of a pair of a first layer formed of a nitride-based semiconductor material containing In, and a second layer formed of a nitride-based semiconductor material, the active layer is formed of a nitride-based semiconductor material containing In And a well layer and a barrier layer formed of a nitride semiconductor material, wherein the first layer of the pair layer includes less indium than the well layer of the active layer.

Description

[0001] LIGHT EMITTING DEVICE [0002]

The present invention relates to a light emitting device, and more particularly, to a nitride-based light emitting device.

A light emitting device (LED) is a type of photoelectric device that is formed in a structure including a p-n junction and converts electrical energy to emit light energy.

The light emitting device can emit light of high brightness at low voltage, compared with other light emitting devices, and has an advantage of high efficiency. In the case of a light emitting device formed of a group III-V nitride semiconductor (hereinafter, referred to as a “nitride-based light emitting device”), light of a wide range of wavelengths including infrared rays or ultraviolet rays is selectively emitted. It may be designed to. Accordingly, the light emitting device can be applied to various devices such as a backlight unit, a display panel, a display device, and a home appliance of a liquid crystal display, and an environment such as arsenic (As) and mercury (Hg). There is an advantage that does not emit harmful substances, has been spotlighted as the next generation light source.

Typical nitride based light emitting devices include an n-type semiconductor layer and a p-type semiconductor layer, and an active layer interposed therebetween. In this case, the n-type semiconductor layer is generally formed of a GaN-based semiconductor material doped with n-type impurities, while the active layer is generally formed of an InGaN-based semiconductor material.

As described above, as the n-type semiconductor layer and the active layer are formed of semiconductor materials having different lattice structures, lattice mismatch exists at an interface between the n-type semiconductor layer and the active layer, and strain is generated.

Due to this strain, the crystallinity of the active layer is deteriorated. In addition, since the influence due to the piezoelectric field is increased and the distance between the wave functions is increased, the recombination rate of electrons and holes is reduced, and the voltage resistance of the light emitting device is lowered.

Further, due to the lattice mismatch present at the interface between the n-type semiconductor layer and the active layer, near the interface between the n-type semiconductor layer and the active layer, a quantum confined stark effect (QCSE) occurs. Due to the quantum confinement stark effect (QCSE), the path of the carriers moving to the active layer is blocked, there is a problem that a blue shift occurs.

Due to the above problems, there is a limit in improving the internal quantum efficiency of the conventional nitride based light emitting device.

The present invention is to solve the above-mentioned problems of the prior art, by mitigating the lattice mismatch according to the difference in indium content, to minimize the strain, to provide a light emitting device that can improve the internal quantum efficiency and the constant voltage characteristics.

According to the present application for achieving the above object, a light emitting device comprising: a first conductivity type semiconductor layer; An intermediate layer formed on the first conductivity type semiconductor layer and including at least one pair layer; An active layer formed on the intermediate layer in a multiple quantum well structure (MQW); And it provides a light emitting device comprising a second conductivity type semiconductor layer formed on the active layer. Here, the pair layer is formed of a pair of a first layer formed of a nitride-based semiconductor material containing indium (In) and a second layer formed of a nitride-based semiconductor material, the active layer is a nitride containing indium (In) And a well layer formed of a semiconductor semiconductor material and a barrier layer formed of a nitride semiconductor material, wherein the first layer of the pair layer includes less indium than the well layer of the active layer.

The light emitting device according to the present invention includes an intermediate layer interposed between the first conductive semiconductor layer and the active layer, the intermediate layer is composed of a plurality of pair layers, each pair layer is a first layer formed of a nitride-based semiconductor material including In And a second layer formed of a nitride semiconductor material. At this time, the first layer of each pair layer contains less indium than the well layer of the active layer.

Accordingly, the intermediate layer can prevent a sudden lattice mismatch between the first conductive semiconductor layer and the active layer, so that the strain between the first conductive semiconductor layer and the active layer can be reduced. Accordingly, the recombination rate of electrons and holes can be improved, and the withstand voltage characteristics can be improved, and the internal quantum efficiency can be improved.

1 is a cross-sectional view showing a light emitting device according to an embodiment of the present application.
2 is a cross-sectional view illustrating an intermediate layer and an active layer illustrated in FIG. 1.
3 to 6 show examples of the bandgap of the intermediate layer and the active layer shown in FIG.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. It should be understood, however, that the present invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In the drawings, the same reference numbers are used throughout the specification to refer to the same or like parts.

Throughout this specification, when a part is referred to as being "connected" to another part, it is not limited to a case where it is "directly connected" but also includes the case where it is "electrically connected" do.

Throughout this specification, when a member is " on " another member, it includes not only when the member is in contact with the other member, but also when there is another member between the two members.

Throughout this specification, when an element is referred to as "including " an element, it is understood that the element may include other elements as well, without departing from the other elements unless specifically stated otherwise. The terms "about "," substantially ", etc. used to the extent that they are used throughout the specification are intended to be taken to mean the approximation of the manufacturing and material tolerances inherent in the stated sense, Accurate or absolute numbers are used to help prevent unauthorized exploitation by unauthorized intruders of the referenced disclosure. The word " step (or step) "or" step "used to the extent that it is used throughout the specification does not mean" step for.

Throughout this specification, the term " combination thereof " included in the expression of the machine form means one or more combinations or combinations selected from the group consisting of the constituents described in the expression of the machine form, And the like.

1 is a cross-sectional view showing a light emitting device according to an embodiment of the present application. 2 is a cross-sectional view showing the intermediate layer and the active layer shown in FIG. 3 to 6 show examples of the band gaps of the intermediate layer and the active layer shown in FIG. 2.

As shown in FIG. 1, the light emitting device 100 according to the exemplary embodiment of the present disclosure may include a buffer layer 120, a first conductive semiconductor layer 130, and an intermediate layer 140 sequentially stacked on the substrate 110. The active layer 150 and the second conductivity type semiconductor layer 160 are included. The light emitting device 100 may include the transparent electrode layer 170 on the second conductive semiconductor layer 160, the first electrode 181 on the first conductive semiconductor layer 130, and the second on the transparent electrode layer 170. It further includes an electrode 182.

The first conductive semiconductor layer 130, the intermediate layer 140, the active layer 150, and the second conductive semiconductor layer 160 may be formed of a group III-V nitride semiconductor. System semiconductor material ".

The substrate 110 may be a growth substrate for growing a nitride based semiconductor. For example, the substrate 110 may be selected from a hetero substrate of any one of Al ₂ O ₃ , SiC, Si, GaAs, ZnS, ZnO, AlN, LiMgO, MgAl ₂ O _3, and InAlGaN, or a homogeneous substrate of GaN. Can be. In particular, the substrate 110 may be a crystal growth substrate made of sapphire (Al ₂ O ₃ ).

The buffer layer 120 may be formed of a substrate 110 due to a difference in lattice structure (or “lattice mismatch”) and thermal expansion coefficient between the substrate 110 and the nitride semiconductor material 130, 140, 150, or 160. It is a buffer layer for reducing crystal defects occurring in the nitride-based semiconductor material (130, 140, 150, 160) grown on the).

The buffer layer 120 may be formed by low temperature growth of an undoped nitride-based semiconductor material. Alternatively, the buffer layer 120 may be formed by low temperature growth of a nitride based semiconductor material doped with the same conductivity type impurities as the first conductivity type semiconductor layer 130 at a lower doping concentration than the first conductivity type semiconductor layer. For example, the buffer layer 120 may be formed of any one of AlInGaN-based semiconductor materials, SiC, and ZnO.

However, although not separately illustrated, when the substrate 110 is selected to be the same material as the nitride semiconductor material, and has the same lattice structure and thermal expansion coefficient as the nitride semiconductor material 130, 140, 150, 160, the substrate 110 may be used. Since the nitride-based semiconductor materials 130, 140, 150, and 160 to be grown on the P-types are less likely to include crystal defects, the light emitting device 100 may not include the buffer layer 120.

The first conductivity type semiconductor layer 130 is formed of a nitride based semiconductor material doped with impurities of the first conductivity type on the buffer layer 120. For example, the first conductivity type semiconductor layer 130 may be n-type GaN doped with n-type impurities such as Si to increase electron mobility.

The intermediate layer 140 is formed of a nitride-based semiconductor material on the first conductive semiconductor layer 130. In this case, the intermediate layer 140 includes indium (In).

The active layer 150 is formed of a single quantum well structure or a multiple quantum well structure (MQW) on the intermediate layer 140.

That is, the active layer 150 includes a well layer formed of a nitride semiconductor material including indium (In), and a barrier layer formed of a nitride semiconductor material. Here, the barrier layer, unlike the well layer, does not include indium (In), but may include a slight amount of indium (In). For example, the well layer may be formed of a semiconductor material having a composition formula of In _z Ga _{1 - z} N (0 <z <1), and the barrier layer may be a composition formula of In _z Ga _{1 - z} N (0 ≦ _z <1). It may be formed of a semiconductor material having a.

In particular, the active layer 150 may be a multi-quantum well structure (MQW) including a plurality of pairs of well layers and barrier layers. For example, the active layer 150 may have a multilayer structure (multi quantum well structure) in which a well layer and a barrier layer are alternately stacked three or more times and five times or less.

The active layer 150 generates light from a combination of electrons and holes injected into the first conductive semiconductor layer 130 and the second conductive semiconductor layer 160, respectively.

In this case, the wavelength region of the light emitted from the light emitting device 100 (hereinafter, referred to as “emission light”) may include a long wavelength to AlN (˜6.4 eV) depending on the content of indium (In) included in the active layer 150. It can be determined in a range of short wavelengths having a band gap. That is, as the active layer 150 contains a larger amount of indium (In), the band gap becomes smaller, and the wavelength region of the emitted light becomes closer to the long wavelength.

In addition, the active layer 150 may be formed of a semiconductor material having a compositional formula (Al _x In _y Ga _(1-xy) N, 0 ≦ x ≦ 1, 0 <y <1) further including aluminum (Al). In this case, the more the active layer 150 contains aluminum (Al), the larger the bandgap, so that the wavelength region of the emitted light is closer to the shorter wavelength.

Meanwhile, as the active layer 150 includes more indium (In), the lattice mismatch between the first conductive semiconductor layer 130 and the active layer 150 becomes larger.

Thus, according to the exemplary embodiment of the present application, the intermediate layer 140 interposed between the first conductivity type semiconductor layer 130 and the active layer 150 is larger than the first conductivity type semiconductor layer 130, and more than the active layer 150. It is formed to contain a small amount of indium (In). In this way, the lattice mismatch between the first conductivity-type semiconductor layer 130 and the active layer 150 may be relaxed by the intermediate layer 140, and the strain may be relaxed. This will be described in more detail below.

The second conductivity type semiconductor layer 160 is formed of a nitride based semiconductor material doped with impurities of a second conductivity type different from the first conductivity type on the active layer 150. For example, the second conductivity-type semiconductor layer 160 may be p-type GaN doped with p-type impurities such as Mg to increase hole mobility.

The transparent electrode layer 170 is formed on the second conductive semiconductor layer 160. The transparent electrode layer 170 is light-transmitting and is selected as a material having a sheet resistance smaller than that of the second conductivity-type semiconductor layer 160, so that the carrier (for example, holes) injected into the second electrode 182 is second. The conductive semiconductor layer 160 is diffused in as wide a region as possible. For example, the transparent electrode layer 170 may be formed of indium tin oxide (ITO), indium zinc oxide (IZO), indium zinc tin oxide (IZTO), indium aluminum zinc oxide (IZAZO), indium gallium zinc oxide (IGZO), IZTO, Metal oxides such as IGTO, AZO, AIO and GZO and the like, and a single layer of any one of metals such as Al, Ag, Pd, Rh and Rt, or any two or more layers or alloys.

The first electrode 181 is formed by removing portions of each of the transparent electrode layer 170, the second conductive semiconductor layer 160, the active layer 150, and the intermediate layer 140, and then expose the first conductive semiconductor layer 130. Is formed on the phase. The first electrode 181 is selected as a material having conductivity, and is directly contacted with the first conductivity type semiconductor layer 130 and electrically connected to the first conductivity type semiconductor layer 130.

The second electrode 182 is formed on the transparent electrode layer 170. The second electrode is selected as a material having conductivity, and is electrically connected to the second conductive semiconductor layer 160 through the transparent electrode layer 170.

However, although not separately illustrated, the second electrode 182 may be formed in direct contact with the second conductivity-type semiconductor layer 160 through a hole passing through the transparent electrode layer 170.

The first and second electrodes 181 and 182 are later used as bonding regions for physically connecting to an external circuit.

Next, the intermediate layer 140 and the active layer 150 according to an embodiment of the present application will be described with reference to FIG. 2.

As shown in FIG. 2, the active layer 150 has a structure in which at least one pair of well layers and barrier layers (hereinafter referred to as “well barrier pairs”) 151, 152, 153, 154, and 155 are sequentially stacked. Is formed.

In exemplary embodiments, the active layer 150 of the multi-quantum structure MQW alternates between the plurality of well layers 151a, 152a, 153a, 154a, and 155a and the plurality of barrier layers 151b, 152b, 153b, 154b, and 155b. The multilayered structure is sequentially stacked. However, this is only an example, and the active layer 150 may have a structure in which a well layer and a barrier layer are alternately stacked two or more times and ten times or less.

The intermediate layer 140 has a structure in which at least one pair layer 141, 142, 143, 144, and 145 are sequentially stacked. Each pair of layers 141, 142, 143, 144, and 145 may be formed of a first layer 141a, 142a, 143a, 144a, which is formed of a nitride-based semiconductor material (eg, InGaN) containing indium (In). 145a) and second layers 141b, 142b, 143b, 144b, and 145b formed of a nitride based semiconductor material (eg, GaN).

In exemplary embodiments, the intermediate layer 140 may include three to five pair layers 141, 142, 143, 144, and 145, and include a plurality of first layers 141a, 142a, 143a, 144a, and 145a. The second layers 141b, 142b, 143b, 144b, and 145b may be a multi-layered structure in which three or more times and five or less times are sequentially stacked alternately with each other.

For reference, FIG. 2 illustrates a case in which the intermediate layer 140 includes five pair layers, and the active layer 150 includes five well barrier pairs. However, this is merely an example, and the intermediate layer 140 may include at least one pair layer, and the active layer 150 may include at least one well barrier pair.

In the intermediate layer 140, the plurality of pair layers 141, 142, 143, 144, and 145 include indium (In) in a lower amount than the adjacent well layer 151a of the active layer 150, and have the same content. Indium (In).

In particular, the first layers 141a, 142a, 143a, 144a, and 145a of each pair layer are formed to include different amounts of indium (In) from each other, and correspondingly, the second layers 141b and 142b of each pair layer. , 143b, 144b, and 145b are formed with different thicknesses from each other.

In addition, the first layers 141a, 142a, 143a, 144a, and 145a of each pair of layers have the same thickness, and range from 1/3 to 1/2 of the thickness of the well layer 151a adjacent to the intermediate layer 140. Can be. Here, when the thickness of the first layers 141a, 142a, 143a, 144a, and 145a is less than 1/3 of the thickness of the well layer 151a, the indium uniformity on the substrate 110 is lowered, thereby reducing the It may lower the reliability.

The first layers 141a, 142a, 143a, 144a, and 145a of each pair layer are formed of a nitride-based semiconductor material including indium (In), like the well layer of the active layer 150, and include a first conductive semiconductor layer ( Indium (In) in an amount corresponding to the range of more than 130 and less than the active layer 150 is included. For example, the first layers 141a, 142a, 143a, 144a, and 145a of each pair layer may be formed of a semiconductor material having a composition formula of In _z Ga _1-z N (0.1 <z <1).

In addition, the second layers 141b, 142b, 143b, 144b, and 145b of each pair layer may have the same or similar amount of indium (In) as one of the barrier layers 151b, 152b, 153b, 154b, and 155b of the active layer 150. ). For example, the second layers 141b, 142b, 143b, 144b, and 145b of each pair layer and the barrier layers 151b, 152b, 153b, 154b, and 155b of the active layer may have an indium (In) content close to 0%. To include, it may be formed of a semiconductor material having a composition formula of In _z Ga _{1 - z} N (0 <z <0.02).

Meanwhile, in the intermediate layer 140, the second layers 141b, 142b, 143b, 144b, and 145b of each pair layer are disposed between the first layers 141a, 142a, 143a, 144a, and 145a and the active layer 150. Barrier layers 151b, 152b, 153b, 154b, and 155b are disposed between well layers 151a, 152a, 153a, 154a, and 155a.

Accordingly, the lattice mismatch and thermal expansion coefficient between the substrate 110 and the nitride semiconductor material are formed by the second layers 141b, 142b, 143b, 144b, and 145b and the barrier layers 151b, 152b, 153b, 154b, and 155b. Decision defects due to differences can be reduced. In addition, the second layers 141b, 142b, 143b, 144b, and 145b and the barrier layers 151b, 152b, 153b, 154b, and 155b may form carriers injected into the first conductive semiconductor layer 130 as active layers 150. ), The operating voltage of the light emitting device 100 can be reduced.

To this end, the second layers 141b, 142b, 143b, 144b, and 145b may be formed of a semiconductor material doped with a first conductivity type like the first conductivity type semiconductor layer 130. At the same time, at least one barrier layer 151b adjacent to the intermediate layer 140 among the barrier layers 151b, 152b, 153b, 154b, and 155b may also be formed of a semiconductor material doped with impurities of a first conductivity type. For example, the second layers 141b, 142b, 143b, 144b, 145b of each pair layer 141, 142, 143, 144, 145 and some barrier layers 151b of the active layer 150 are n such as Si. It may be a nitride-based semiconductor material doped with -type impurities.

Next, examples of the intermediate layer 140 will be described with reference to FIGS. 3 to 6.

As illustrated in FIG. 3, the plurality of pair layers 141, 142, 143, 144, and 145 included in the intermediate layer 140 are smaller than the bandgap of the first conductivity-type semiconductor layer 130 and the active layer 150. Is a bandgap larger than the bandgap The plurality of pair layers 141, 142, 143, 144, and 145 may include the first layers 141a, 142a, 143a, 144a, and 145a having different band gaps, and the second layers 141b and 142b having different thicknesses. , 143b, 144b, and 145b. Here, the first layers 141a, 142a, 143a, 144a, and 145a of each pair layer are band gaps that fluctuate with an irregular difference as the first conductive semiconductor layer 130 approaches the active layer 150.

That is, the first layers 141a, 142a, 143a, 144a, and 145a of each pair layer have an indium (In) content that varies with an irregular difference as the first conductive semiconductor layer 130 moves closer to the active layer 150. ). Corresponding to the indium content of each of the first layers 141a, 142a, 143a, 144a, and 145a, the second layers 141b, 142b, 143b, 144b, and 145b of each pair layer also have a first conductivity type semiconductor layer 130 The closer to the active layer 150 from), the thickness varies with an irregular difference.

For example, as shown in FIG. 3, the first layer 141a of the first pair layer adjacent to the first conductivity type semiconductor layer 130 of the intermediate layer 140 includes a relatively high first content of indium, Assuming that the first layer 145a of the fifth pair layer adjacent to the active layer 150 contains indium of a second content lower than the first content, the second layer 141b of the first pair layer is of a first content. While the second layer 145b of the fifth pair layer is formed to have a first thickness corresponding to indium, the second layer 145b of the fifth pair layer is formed to have a second thickness that is thinner than the first thickness, corresponding to a second content of indium lower than the first content.

As described above, between the first conductivity type semiconductor layer 130 and the active layer 150, an indium (In) having a content varying irregularly in a range higher than the first conductivity type semiconductor layer 130 and lower than the active layer 150. The intermediate layer of the multi-layer structure in which the first layers 141a, 142a, 143a, 144a, and 145a including the interlayer are sandwiched between the second layers 141b, 142b, 143b, 144b and 145b containing no indium (In). 140 may be intervened. At this time, the thickness of the second layer (141b, 142b, 143b, 144b, 145b) is proportional to the indium content of the first layer (141a, 142a, 143a, 144a, 145a), respectively, and the first layer (141a, 142a, 143a). , 144a and 145a, the higher the indium content of the second layer (141b, 142b, 143b, 144b, 145b) is formed in a thicker thickness, the indium content of the first layer (141a, 142a, 143a, 144a, 145a) The lower the second layers 141b, 142b, 143b, 144b, and 145b are formed in a thinner thickness, and each pair layer 141, 142, 143, 144, and 145 includes the same amount of indium (In). As a result, lattice mismatching at each interface corresponding to the first conductivity-type semiconductor layer 130 and the active layer 150 may be relaxed.

Alternatively, as illustrated in FIG. 4, the plurality of pair layers 141, 142, 143, 144, and 145 included in the intermediate layer 140 are smaller than the band gap of the first conductivity type semiconductor layer 130 and are active layers. It is a band gap larger than the band gap of 150. The plurality of pair layers 141, 142, 143, 144, and 145 may include the first layers 141a, 142a, 143a, 144a, and 145a having different band gaps, and the second layers 141b and 142b having different thicknesses. , 143b, 144b, and 145b. Here, the first layers 141a, 142a, 143a, 144a, and 145a of each pair layer gradually increase in size at regular intervals and gradually decrease as they approach the active layer 150 from the first conductivity-type semiconductor layer 130. Bandgap.

In other words, the first conductive semiconductor layer 130 and the first pair 141a and 145a of the fifth pair layer adjacent to the first conductive semiconductor layer 130 and the active layer 150 are interposed therebetween. The band gap is lower than that of the first layers 142a, 143a, and 144a of the other second to fourth pair layers.

That is, the first layers 141a, 142a, 143a, 144a, and 145a of each pair layer gradually decrease as the closer to the active layer 150 from the first conductivity type semiconductor layer 130, and gradually increase in number. And varying amounts of indium (In). Corresponding to the indium content of the first layers 141a, 142a, 143a, 144a, and 145a of each pair layer, the second layers 141b, 142b, 143b, 144b, and 145b of each pair layer are the first conductivity type semiconductors. As the layer 130 moves closer to the active layer 150, the thickness becomes thinner and gradually thicker at regular intervals.

Specifically, the first and fifth pair layers 141 and 145 adjacent to the first conductivity-type semiconductor layer 130 and the active layer 150 of the intermediate layer 140 may have other second to fourth intervening layers therebetween. First layers 141a and 145a formed to contain indium (In) in a higher content than the first layers 142a, 143a and 144a of the pair layer, and second layers 142b and 143b of the second to fourth pair layers. And second layers 141b and 145b formed to a thickness greater than 144b.

The second and fourth pair layers 142 and 144 adjacent to the first pair layer 141 and the fifth pair layer 145 of the intermediate layer 140 are formed of the third pair layer interposed therebetween. A second layer 142b formed to a thickness thicker than the first layers 142a and 144a formed to contain indium (In) in a higher content than the first layer 143a and the second layer 143b of the third pair layer, 144b).

As described above, between the first conductivity-type semiconductor layer 130 and the active layer 150, gradually decreases with a regular difference in a range higher than the first conductivity-type semiconductor layer 130 and lower than the active layer 150. First layers 141a, 142a, 143a, 144a, 145a containing an indium (In) content are sandwiched between second layers 141b, 142b, 143b, 144b, 145b without indium (In) The intermediate layer 140 having a multilayer structure may be interposed. At this time, the thickness of the second layer (141b, 142b, 143b, 144b, 145b) is proportional to the indium content of the first layer (141a, 142a, 143a, 144a, 145a, respectively, each pair included in the intermediate layer 140 Layers 141, 142, 143, 144, and 145 contain the same amount of indium (In). As a result, lattice mismatching at each interface corresponding to the first conductivity-type semiconductor layer 130 and the active layer 150 may be relaxed.

Alternatively, as illustrated in FIG. 5, the plurality of pair layers 141, 142, 143, 144, and 145 included in the intermediate layer 140 are smaller than the band gap of the first conductivity type semiconductor layer 130 and are active layers. It is a band gap larger than the band gap of 150. The plurality of pair layers 141, 142, 143, 144, and 145 may include the first layers 141a, 142a, 143a, 144a, and 145a having different band gaps, and the second layers 141b and 142b having different thicknesses. , 143b, 144b, and 145b. Here, the first layers 141a, 142a, 143a, 144a, and 145a of each pair layer are band gaps that gradually increase with a regular difference as the first conductive semiconductor layer 130 approaches the active layer 150.

In other words, the first layer 141a of the first pair layer adjacent to the first conductivity type semiconductor layer 130 among the intermediate layers 140 may include the first layers 142a, 143a, of the other second to fifth pair layers. The first layer 145a of the fifth pair layer adjacent to the active layer 150 has a lower bandgap than 144a and 145a, and the first layers 141b, 142b, 143b, and 144b of the other first to fourth pair layers. Higher bandgap.

That is, the content of the first layers 141a, 142a, 143a, 144a, and 145a of each pair layer gradually decreases with a regular difference as the first conductive semiconductor layer 130 approaches the active layer 150. Indium (In). Corresponding to the indium content of the first layers 141a, 142a, 143a, 144a, and 145a of each pair layer, the second layers 141b, 142b, 143b, 144b, and 145b of each pair layer are the first conductivity type semiconductors. The closer to the active layer 150 from the layer 130, the thinner the thickness becomes at regular intervals.

As a result, lattice mismatching at each interface corresponding to the first conductivity-type semiconductor layer 130 and the active layer 150 may be relaxed.

Alternatively, as illustrated in FIG. 6, the plurality of pair layers 141, 142, 143, 144, and 145 included in the intermediate layer 140 are smaller than the band gap of the first conductive semiconductor layer 130, and the active layer. It is a band gap larger than the band gap of 150. The plurality of pair layers 141, 142, 143, 144, and 145 may include the first layers 141a, 142a, 143a, 144a, and 145a having different band gaps, and the second layers 141b and 142b having different thicknesses. , 143b, 144b, and 145b. Here, the first layers 141a, 142a, 143a, 144a, and 145a of each pair layer are band gaps that gradually decrease with a regular difference as the first conductive semiconductor layer 130 approaches the active layer 150. . Correspondingly, the second layers 141b, 142b, 143b, 144b, and 145b of each pair layer are gradually increasing in thickness.

That is, the first layers 141a, 142a, 143a, 144a, and 145a of each pair layer include a smaller amount of indium (In) as the closer to the first conductivity type semiconductor layer 130, and the closer to the active layer 150. The higher the amount of indium (In) is included. The second layers 141b, 142b, 143b, 144b, and 145b of each pair layer are thinner as they are closer to the first conductivity-type semiconductor layer 130, and thicker as they are closer to the active layer 150.

In this case, the first pair layer 141 in contact with the first conductivity-type semiconductor layer 130 has a smaller amount of indium (In) than the first layers 142a, 143a, 144a, and 145a of the other second to fifth pair layers. ) And a second layer 141b that is thinner than the second layers 142b, 143b, 144b, and 145b of the other second to fifth pair layers. For example, similar to the first conductivity type semiconductor layer 130, the first layer 141a of the first pair layer may have an energy band gap corresponding to ultraviolet light (UV).

On the other hand, the fifth pair layer 145 in contact with the active layer 150 includes a first indium (In) having a higher content than the first layers 141a, 142a, 143a, and 144a of the other first to fourth pair layers. Layer 145a, and a second layer 145b thicker than the second layers 142b, 143b, 144b, 145b of the other first to fourth pair layers.

By way of example, the first layers 141a, 142a, 143a, 144a, 145a of each pair layer include indium in increasing amounts in a linear function, and at the same time, the second layers 141b, 142b of each pair layer. , 143b, 144b, and 145b may be gradually increasing thicknesses as a linear function.

That is, assuming that the first layer 141a of the first pair layer includes indium of n * a content, the first layers 142a, 143a, 144a, and 145a of the second to fifth pair layers are respectively ( n + 1) * a, (n + 2) * a, (n + 3) * a, and (n + 4) * a indium. In addition, assuming that the second layer 141b of the first pair layer is m * b thick, the second layers 142b, 143b, 144b, and 145b of the second to fifth pair layers are (m + 1). It may be a thickness of * b, (m + 2) * b, (m + 3) * b, and (m + 4) * b.

This is described again as a numerical example as follows.

It is assumed that the well layer and the barrier layer adjacent to the intermediate layer 140 of the active layer 150 have a thickness of 30 μs and 45 μm, respectively, and the well layer adjacent to the intermediate layer 140 includes 15.0% of indium (In). The intermediate layer 140 is a first pair layer stacked on the first conductivity type semiconductor layer 130, a second pair layer stacked on the first pair layer, and a third layer stacked on the second pair layer adjacent to the active layer 150. It is assumed that three pair layers corresponding to the pair layers are included.

In this case, the first pair layer, the second pair layer, and the third pair layer are higher than the content (0%) of indium (In) included in the first conductivity-type semiconductor layer 130 and indium (In) included in the active layer 150. Within a range lower than the content of 15.0%, each contains the same content (for example, 4%) of indium (In).

In this case, the first layer of the first pair layer, the second pair layer, and the third pair layer may include indium (In) in an amount of 7.5%, 10%, and 12.5%, respectively, gradually increasing. Correspondingly, the second layer of the first pair layer, the second pair layer, and the third pair layer may be formed with increasing thicknesses of 24 μs, 36 μs, and 48 μs, respectively. In addition, the first layer of the first pair layer, the second pair layer, and the third pair layer is formed with the same thickness of 12 mm 3, which is less than 1/2 of the thickness of the well layer adjacent to the intermediate layer 140, and the first pair layer, the second pair layer And the second layer of the third pair layer may include 0% of indium (In) as the barrier layer adjacent to the intermediate layer 140.

As described above, the intermediate layer 140 between the first conductivity-type semiconductor layer 130 and the active layer 150 includes indium (In) in an incrementally increasing content within a lower range than the active layer 150, Interface between the first conductivity type semiconductor layer 130 and the intermediate layer 140, between each pair layer 141, 142, 143, 144, 145 in the intermediate layer 140, and between the intermediate layer 140 and the active layer 150. The lattice mismatch that occurs on the edges is relatively small and can occur with a gentle gap. Accordingly, the lateral strain due to lattice mismatch of large and sudden gaps can be further alleviated.

Due to the relaxation of the lateral strain (laternal strain), the crystallinity of the active layer 150 can be further improved. In addition, since the influence due to the piezoelectric field can be reduced, the distance between the wave functions is reduced, thereby improving the recombination rate of electrons and holes. In addition, the constant voltage characteristic of the light emitting device 100 may be improved.

In addition, since the quantum confinement stark effect due to the large and sudden gap lattice mismatch can be reduced, it is possible to prevent the path blocking of carriers due to the quantum confinement stark effect, thereby reducing the blue shift. That is, the width of the wavelength change can be reduced.

In addition, under the condition of not departing from the above range, the number of pair layers included in the intermediate layer 140, the average indium content relative to the thickness of each pair layer, and the thickness of each pair layer may be freely determined.

For example, based on a light emitting device having a size of 600 × 500 μm / cm 2, a comparative example does not include the intermediate layer 140, an optical power corresponding to each embodiment of the present application including the intermediate layer 140, The reverse current (current to -5V), and electrostatic discharge (ESD), where "electrostatic discharge" means "the ratio of devices not destroyed by high current applied over time", each experiment The conditions were compared in the same state.

Accordingly, the light emitting device according to the embodiment has an optical power of 57.6 kV increased by about 2.1 kW from the optical power (55.5 kV) of the comparative example, a reverse current of 0.01 reduced by about 0.14 from the reverse current (0.15) of the comparative example, and comparison It was confirmed that the electrostatic discharge of 82% was increased from the electrostatic discharge (0%) of the example.

As described above, the light emitting device according to the exemplary embodiment of the present application may mitigate lattice mismatch between the first conductivity-type semiconductor layer 130 and the active layer 150 by including the intermediate layer 140, thereby improving internal quantum efficiency. Since it can be improved, in terms of optical power Po, reverse current Ir, and electrostatic discharge ESD, it can exhibit improved characteristics than the comparative example.

The method of manufacturing the light emitting device 100 shown in FIGS. 1 and 2 is as follows.

First, a substrate 110 selected from a hetero substrate of any one of Al ₂ O ₃ , SiC, Si, GaAs, ZnS, ZnO, AlN, LiMgO, MgAl ₂ O _3, and InAlGaN, or a homogeneous substrate of GaN is prepared. .

The nitride-based semiconductor material is grown on the substrate 110 to form the buffer layer 120, the first conductive semiconductor layer 130, the intermediate layer 140, the active layer 150, and the second conductive semiconductor layer 160. do.

At this time, the growth of the nitride-based semiconductor material is any one of metal organic chemical vapor deposition (MOCVD), molecular beam growth (MBE) and hydride vapor deposition (HVPE). Can be implemented. In particular, the growth of the nitride-based semiconductor material may be performed by metal organic chemical vapor deposition (MOCVD).

The buffer layer 120 may be formed of any one of InAlGaN-based semiconductor materials, SiC, and ZnO grown on the substrate 110. In particular, the buffer layer 120 may be an InAlGaN-based semiconductor material.

The first conductivity type semiconductor layer 130 is formed by growing a nitride semiconductor material (eg, n-GaN) doped with n-type impurities such as Si on the buffer layer 120. In this case, a source for growing the first conductivity type semiconductor layer 130 may be selected as an inert gas such as SiH ₄ , Si ₂ H _4, or the like.

The intermediate layer 140 alternately grows a semiconductor material having a composition formula of In _z Ga _{1 - z} N (0.1 <z <1) and a semiconductor material having a composition formula of In _z Ga _1-z N (0 <z <0.02). The first layer 141a, 142a, 143a, 144a, 145a and the second layer 141b, 142b, 143b, 144b, 145b are alternately and repeatedly stacked several times.

At this time, the indium content (z) of the In _z Ga _1-z N (0.1 <z <1) semiconductor material is gradually increased from the beginning to the end of the formation process of the intermediate layer 140. Accordingly, the first layers 141a, 142a, 143a, 144a, and 145a of the at least one pair layer 141, 142, 143, 144, and 145 included in the intermediate layer 140 may be formed of a first conductive semiconductor layer ( 130 includes indium of a gradually decreasing content, and adjacent to the active layer 150 includes an indium of a gradually increasing content, resulting in a gradually increasing energy band gap.

In this case, the second layers 141b, 142b, 143b, 144b, and 145b may be doped with n-type impurities.

The active layer 150 may be formed as a single quantum well structure or a multi quantum well structure on the intermediate layer 140. When the active layer 150 is a multi quantum well structure, the plurality of well layers 151a, 152a, 153a, and 154a may be formed. , 155a and the plurality of barrier layers 151b, 152b, 153b, 154b, and 155b are alternately stacked and repeated a plurality of times.

In this case, the well layers 151a, 152a, 153a, 154a, and 155a may be formed of a semiconductor material having a composition formula of In _z Ga _{1 - z} N (0.1 <z <1), and the barrier layers 151b, 152b, and 153b. , 154b and 155b may be formed of a semiconductor material having a composition formula of In _z Ga _{1 - z} N (0 <z <0.5).

For example, the well layer 151a disposed closest to the intermediate layer 140 of the active layer 150 may be formed to have a thickness of 3.0 nm with the indium source flow rate (TMIn MFC) adjusted to 360. The first layer of any one of the pair layers 140 is formed to a thickness of 1.2 nm thinner than the well layer 151a while adjusting the flow rate of the indium source (TMIn MFC) to 36, which is 1/10 of the well layer 151a. Can be.

The second conductive semiconductor layer 160 is formed by growing a nitride semiconductor material (eg, p-GaN) doped with a p-type impurity such as Mg on the active layer 150.

In this case, in the growth of the second conductivity-type semiconductor layer 160, the source of Ga may be trimethylgallium (TMGa) or triethylgallium (TEGa), and the source of N may be ammonia (NH _3). ) Or dimethylhydrazine (DMHy).

Subsequently, the transparent conductive material is laminated on the second conductive semiconductor layer 160 to form the transparent electrode layer 170. A portion of each of the transparent electrode layer 170, the second conductive semiconductor layer 160, the active layer 150, and the intermediate layer 140 is removed to expose the first conductive semiconductor layer 130. Thereafter, a first electrode 181 is formed on the exposed first conductive semiconductor layer 130, and a second electrode 182 is formed on the transparent electrode layer 170.

 It will be understood by those of ordinary skill in the art that the foregoing description of the embodiments is for illustrative purposes and that those skilled in the art can easily modify the invention without departing from the spirit or essential characteristics thereof. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive. For example, each component described as a single entity may be distributed and implemented, and components described as being distributed may also be implemented in a combined form.

The scope of the present invention is defined by the appended claims rather than the detailed description, and all changes or modifications derived from the meaning and scope of the claims and their equivalents should be construed as being included within the scope of the present invention.

100: light emitting element
130: first conductive semiconductor layer
140: middle layer
141, 142, 143, 144, and 145: first to fifth pair layers
141a, 142a, 143a, 144a, and 145a: first layer of each of the first to fifth pair layers
141b, 142b, 143b, 144b, and 145b: second layer of each of the first to fifth pair layers
150: active layer
151, 152, 153, 154, 155: Well barrier pair
151a, 152a, 153a, 154a, 155a: well layer
151b, 152b, 153b, 154b, 155b: barrier layer
160: second conductivity type semiconductor layer

Claims (10)

In the light emitting device,
A first conductivity type semiconductor layer;
An intermediate layer formed on the first conductivity type semiconductor layer and including at least one pair layer;
An active layer formed on the intermediate layer in a multiple quantum well structure (MQW); And
Including a second conductive semiconductor layer formed on the active layer,
The pair layer is formed of a pair of a first layer formed of a nitride-based semiconductor material containing In, and a second layer formed of a nitride-based semiconductor material,
The active layer includes a well layer formed of a nitride-based semiconductor material including In, and a barrier layer formed of a nitride-based semiconductor material.
The first layer of the fair layer is a light emitting device containing less indium than the well layer of the active layer. The method of claim 1,
The at least one pair layer includes indium in different amounts of mutually different light emitting devices. 3. The method of claim 2,
The at least one pair layer includes a first pair layer in contact with the first conductivity type semiconductor layer, and a second pair layer in contact with the active layer,
The first layer of the second pair layer is a light emitting device comprising a greater amount of indium than the first layer of the first pair layer. The method of claim 3, wherein
The thickness of the second layer of the second pair layer is greater than the thickness of the second layer of the first pair layer. The method of claim 4, wherein
Wherein the first thickness is 1/3 to 1/2 the thickness of the well layer of the active layer. 3. The method of claim 2,
The at least one pair layer includes indium in an amount gradually decreasing adjacent to the first conductivity type semiconductor layer, and a light emitting element comprising an indium gradually increasing in proximity to the active layer. The method according to claim 6,
And the second layer of each of the at least one pair layer includes indium in the same amount as the barrier layer of the active layer. The method according to claim 6,
The at least one pair layer is a thickness corresponding to the content of the indium,
A light emitting device comprising the second layer of a thinner thickness closer to the first conductivity type semiconductor layer, and the second layer of a thicker thickness closer to the active layer. 9. The method according to any one of claims 2 to 8,
The intermediate layer is a light emitting device having a multilayer structure in which the first and second layers are alternately stacked three times or more and five times or less sequentially. The method of claim 9,
The first layer of the intermediate layer is formed of a semiconductor material having a composition formula of In _z Ga _{1 - z} N (0.1 <z <1),
And the second layer of the intermediate layer is formed of a semiconductor material having a composition formula of In _z Ga _{1 - z} N (0 <z <0.02).

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