CN101587927B - Light emitting element and manufacturing method thereof - Google Patents

Abstract

The invention discloses a light-emitting element and a manufacturing method thereof. The element is a semiconductor element and comprises a growth substrate, wherein the growth substrate is sequentially provided with an epitaxial structure of an n-type semiconductor layer, a quantum well active layer, a p-type semiconductor layer and the like, and then the quantum well active layer of the light-emitting element is not required to be etched through an etching process by combining the internal diffusion effect of a quantum well on the basis of the holography exposure technology, namely the photonic crystal with two-dimensional space periodicity dielectric constant change or material composition change. The photonic crystal structure is formed by combining two incident lights to interfere the quantum well active layer to cause an internal diffusion effect based on a full-image exposure technology. The photonic crystal light-emitting element can not only increase the internal quantum effect, but also increase the light extraction efficiency.

Description

Light emitting element and manufacturing method thereof

technical field

The invention relates to a structure of a light-emitting element and a manufacturing method thereof.

Background technique

Semiconductor light-emitting components are widely used, such as traffic signal signs, Blue-DVD high-density storage, HD-DVD, green RCLED (applicable to internal communication and control systems of plastic optical fibers used in vehicles), and medical devices (UV LEDs), etc. The improvement of the performance of the light-emitting element will make the application of the light-emitting element more extensive, for example, it can be applied to optical display devices (RGB edge-lit back light units) or rear-projection TV (Rear-projection TV). Therefore, improving device performance is a major research topic at present.

Because light emitting diodes have no directionality, the light use efficiency is also limited due to the influence of etendue in the application of optical modules. Therefore, making the light emission of the light emitting diodes directional, thereby reducing the divergence angle, is also one of the ways to improve the efficiency of the light emitting diodes. E. Yablonovitch and S. John proposed in 1987 that a medium with a period of 1/2 the wavelength scale of electromagnetic waves, that is, the wavelength of far-infrared rays to visible light (300-700nm), can make electromagnetic waves have a high degree of order here. The behavior in materials can be controlled by the spatial structure, arrangement period, structural form and dielectric constant of the medium just like electrons in crystals, so there is no need to change the chemical structure of the medium itself, only the wavelength scale of the medium and the photon energy gap Components with different optical characteristics can be manufactured by design. This new type of artificial crystal is called Photonic Crystal (PC). If it is applied to light-emitting diodes, the hole-like structure of two-dimensional photonic crystals is etched on its surface, so that the light confined in the light-emitting diodes can no longer be emitted in any direction, which greatly increases the chance of light-guided upward emission, thereby reducing the divergence of light-emitting diodes. angle and improve its efficiency.

The composition of photonic crystals will show periodic changes in the xy plane. Observe this structure on a two-dimensional equivalent refractive index plane, as shown in Figure 1, and present the equivalent refractive index of this structure in a two-dimensional manner, where n ₁ is the refractive index after the internal diffusion effect of the quantum well, and n ₂ is the refractive index before the internal diffusion effect of the quantum well. We define the equivalent refractive index difference (n ₁ -n ₂ ) as Δn,

Δn=n _r +j*n _i (1-1)

Where n _r is the real part of the equivalent refractive index difference, and _ni is the imaginary part of the equivalent refractive index difference. The material composition of the active layer changes periodically, and the two parameters of n _r and _ni will exist at the same time. n _r affects the light extraction efficiency of the LED, and the value of _ni affects the internal efficiency of the LED. It is known that a two-dimensional photonic crystal is etched on the surface of the light-emitting diode to form a similar two-dimensional equivalent refractive index plane, but its Δn only exists n _r (n _i is zero), so this structure can only affect the light extraction of the light-emitting diode Efficiency and divergence angle.

Another known method is to use a traditional laser holography exposure device (Laser holography apparatus), and use semiconductor process exposure, development and etching methods to form nano-scale island structures (nano-sized islands) on the ohmic contact layer of the light-emitting element. ) to increase the light extraction efficiency of the light-emitting element.

Contents of the invention

The invention provides a light-emitting element with a photonic crystal structure, comprising: a substrate; and a semiconductor epitaxial structure located on the substrate, wherein the semiconductor epitaxial structure has a quantum well active layer, and the quantum well active layer is contained in a one-dimensional Or the two-dimensional space has a photonic crystal structure with periodic dielectric constant changes, and the photonic crystal structure is only formed in the active layer of the quantum well. Taking light-emitting diodes as an example, the composition of the active layer material will show periodic changes in the X-Y plane, which can increase the internal quantum effect and light extraction efficiency of light-emitting diodes at the same time. In addition, the periodic change of its refractive index occurs in the active layer instead of the surface of the light-emitting diode. According to the distribution of photons, the photonic crystal light-emitting diode can effectively improve its internal quantum effect and light extraction with only a small amount of change in the refractive index. efficiency.

Description of drawings

Figure 1 is a diagram showing that the composition of the light-emitting diode gain region material changes periodically on the X-Y plane;

Fig. 2 is a structural diagram showing the novel holographic exposure system designed by the present invention;

Fig. 3 is a diagram showing the local quantum mixing effect caused by the incident light of the present invention;

Figure 4a is a diagram showing the energy band distribution before the diffusion effect inside the quantum well;

Figure 4b is a diagram showing the distribution of energy bands after the internal diffusion effect of the quantum well;

Fig. 5 is a diagram showing the intensity distribution of the light field of the present invention;

Fig. 6a is a diagram showing the epitaxial structure of a light emitting diode according to an embodiment of the present invention;

Figure 6b is a photonic crystal light-emitting diode showing an embodiment of the present invention;

Fig. 7 is a graph showing the composition of the active layer in the light-emitting diode according to the embodiment of the present invention along the X-axis direction;

FIG. 8 is a side view showing the structure of a photonic crystal light-emitting diode according to an embodiment of the present invention.

Explanation of reference signs

1 Growth substrate 2 n-type semiconductor layer

3 multiple quantum well structure 4 p-type semiconductor layer

5 Composition before the internal diffusion effect of the quantum well 6 Composition after the internal diffusion effect of the quantum well

7 Current spreading layer 8 n-type electrode

9 p-type electrode 201 laser source (laser source)

202 1:10 beam splitter (splitter) 203 1:1 beam splitter (splitter)

204 100% UV mirror 205 Power monitor

206 automatic shutter

207 X-Y motion controller

208 wafer seat rotation frame (rotation stage)

209 Rotator A(rotator) 210 Rotator B(rotator)

211 wafer test piece a incident light 1

b incident light 2 c high light intensity area

d Low light intensity area d ₁ Distance between 1:1 beam splitter and 100% UV mirror

E _c conduction band energy E _v valence band energy

E _g , E _g ' energy band difference n ₁ Refractive index after internal diffusion effect of quantum well

Refractive index before the internal diffusion effect of n ₂ quantum well

The period of Λ light intensity distribution Ψ The included angle of the internal diffusion effect of the secondary quantum well

Detailed ways

In order to prevent the etching process from causing damage to the active layer region of the epitaxial structure, a novel holographic exposure system as shown in FIG. 2 is now used to illustrate an embodiment of the present invention. A 1:1 beam splitter (Splitter) 203 is used to replace the beam expander (Beam Expander) in the traditional system, and the wafer holder rotating frame 208 is set on the precise two-axis electric controller (XY Motion Controller) 207 . The two incident lights a and b with optical path difference will form a one-dimensional periodic light intensity distribution on the surface of the LED chip 211 , as shown in FIG. 3 . The period Λ of light intensity distribution can be determined by formula 1-2. Among them, λ _laser is the wavelength of the laser, d ₁ is the distance between the 1:1 beam splitter and the 100% UV mirror, n is the optical path difference factor caused by the beam splitting, m is the order of two light interferences, and n and m are integer.

λ _Laser ＝2m[(d ₁ /λ _Laser )-n-Λcosθ] (1-2)

Before production, the interference fringes of the two incident lights must be recorded on the photoresist (fixed θ and m=1), and the interference period Λ is measured by AFM, and the optical path difference factor n is deduced inversely, and then passed through the rotator A (Rotator) 209 changes the angle θ to determine the period Λ, where θ can be between 20-80 degrees.

The present invention uses two incident light interferences to achieve light intensity changes with a period of 200nm to 1000nm, and then controls the light intensity and the length of incident light time to control different degrees of energy gap changes and refractive index changes. When the incident light penetrates the confinement layer of the photoelectric element and is absorbed by the quantum well, the local temperature of the quantum well rises rapidly, causing the internal component atoms to become unstable due to heat absorption. When the atom absorbs too much heat energy, it will break free from the original The bound covalent bonds begin to diffuse toward lower concentrations. This effect is called Quantum Well Interdiffusion (QWI). Generally speaking, the energy band diagram of the quantum well in the active layer is a rectangular well shape (as shown in Figure 4a), and after the internal diffusion effect, the energy band distribution of the quantum well is in a smooth arc shape (as shown in Figure 4b), And the energy band difference E _g ' also becomes larger. As the luminous wavelength shifts toward shorter wavelengths, the refractive index decreases accordingly. The interference of two incident lights will produce a one-dimensional and equal-period light intensity distribution. To make a two-dimensional photonic crystal, two interference steps can be performed, and the rotator B (Rotator) 210 in Figure 2 is used to determine the two quantum wells. The included angle Ψ of the diffusion effect (can be between 20-90 degrees), and at the same time, by controlling the light intensity, the area (intersection) that repeats the internal diffusion effect of the quantum well has a large energy difference (as shown in the c point area of Figure 5), Furthermore, the amount of change in the refractive index occurs. The amount of change has a two-dimensional spatial periodicity, and the two-dimensional period does not need to be consistent. When fabricating two-dimensional photonic crystal light-emitting diodes according to this method, it is necessary to control the time difference between the two interferences to avoid temperature drop caused by too long time difference and affect the internal diffusion effect of the quantum well. In addition, the carrier of the light-emitting diode chip can also be heated to enhance the effect of the internal diffusion effect of the quantum well. Generally, the size of the laser beam is about 1 mm, and the area that can cause the internal diffusion effect of the quantum well is limited. A large-area photonic crystal light-emitting diode is fabricated in a progressive manner, as shown in Figure 6b. FIG. 7 shows the composition (y) distribution of the active layer along the X axis after the light-emitting element undergoes a quantum well internal diffusion effect. Since the light energy distribution will show a periodic and gradual change with the space (XY), the active layer composition (y) after the internal diffusion effect of the secondary quantum well will also show a periodic and gradual change with the space (XY). , thereby increasing the optical confinement and current confinement of the LED.

(Embodiment 1)

As shown in Figure 6a, the growth substrate 1 can be made of gallium arsenide, silicon, silicon carbide, aluminum oxide, indium phosphide, gallium phosphide, aluminum nitride or gallium nitride, etc. Optical substrate or light-absorbing substrate; grow n-type semiconductor layer 2 (such as n-GaN, n-AlGaInP), multi-quantum well active layer 3 (such as InGaN, AlGaInP), and p-type semiconductor layer sequentially by metalorganic chemical vapor phase epitaxy 4 (such as p-GaN, p-AlGaInP) and other layers to form a light-emitting diode epitaxial structure, wherein the n-type semiconductor layer and the p-type semiconductor layer can be used as confinement layers. Using the new holographic exposure system structure shown in Figure 2, the two incident lights are directly cast on the entire surface of the light-emitting diode to form interference fringes. Between the wavelengths corresponding to the well active layer structure 3 (λ _cladding <λ _laser <λ _QW ), the incident light will penetrate the confinement layer (p-type semiconductor layer) and be absorbed by the multi-quantum well active layer, so that the local quantum wells rapidly When the temperature rises, the constituent atoms inside the chip become unstable due to heat absorption. When the atoms absorb too much heat energy, they will break free from the covalent bonds that were originally bound, and begin to diffuse to lower concentrations, resulting in the internal diffusion effect of the quantum well. . The two incident light interferences can achieve light intensity changes with a period of 200nm-1000nm, and then by controlling the light intensity and the length of the incident light time, different degrees of energy gap changes and refractive index changes can be controlled. Then use the rotator (Rotator) B to determine the angle Ψ of the internal diffusion effect of the two quantum wells (can be between 20-90 degrees) according to the requirements. Also by controlling the light intensity, the area where the internal diffusion effect of the quantum well is repeated (intersection) ) has a large energy difference, which in turn produces a change in the refractive index. The amount of change has a two-dimensional spatial periodicity, and the two-dimensional period does not need to be consistent, that is, a photonic crystal light-emitting element (as shown in FIG. 6b ) is formed. A current spreading layer 7 is then formed on the p-type semiconductor layer, and after the current spreading layer is etched down to the n-type semiconductor layer, a p-type electrode 9 and an n-type electrode 8 are respectively formed on the current spreading layer and the n-type semiconductor layer , that is, a photonic crystal light-emitting diode element is formed, as shown in FIG. 8 .

(Example 2)

As shown in Figure 6a, the growth substrate 1 can be made of gallium arsenide, silicon, silicon carbide, aluminum oxide, indium phosphide, gallium phosphide, aluminum nitride or gallium nitride, etc. Optical substrate or light-absorbing substrate; grow n-type semiconductor layer 2 (such as n-GaN, n-AlGaInP), multi-quantum well active layer 3 (such as InGaN, AlGaInP), and p-type semiconductor layer sequentially by metalorganic chemical vapor phase epitaxy 4 (such as p-GaN, p-AlGaInP) and other layers to form a light-emitting diode epitaxial structure, wherein the n-type semiconductor layer and the p-type semiconductor layer can be used as confinement layers. Using the new holographic exposure system structure in Figure 2, the two incident lights are directly cast on the entire surface of the light-emitting diode to form interference fringes. λ _laser <λ _cladding ), the incident light will be absorbed by the surface of the confinement layer (p-type semiconductor layer) to generate local high temperature, and the internal diffusion effect of the quantum well will be generated through thermal diffusion. The two incident light interferences can achieve light intensity changes with a period of 200nm-1000nm, and then by controlling the light intensity and the length of the incident light time, different degrees of energy gap changes and refractive index changes can be controlled. Then use the rotator (Rotator) B to determine the included angle Ψ of the internal diffusion effect of the two quantum wells (can be between 20-90 degrees) according to the requirements, and also control the light intensity to make the area where the internal diffusion effect of the quantum well is repeated (intersection) ) has a large energy difference, which in turn produces a change in the refractive index. The amount of change has a two-dimensional spatial periodicity, and the two-dimensional period does not need to be consistent, that is, a photonic crystal light-emitting element (as shown in FIG. 6b ) is formed. A current spreading layer 7 is then formed on the p-type semiconductor layer, and after the current spreading layer is etched down to the n-type semiconductor layer, a p-type electrode 9 and an n-type electrode 8 are respectively formed on the current spreading layer and the n-type semiconductor layer , that is, a photonic crystal light-emitting diode element is formed, as shown in FIG. 8 .

(Embodiment 3)

As shown in Figure 6a, the growth substrate 1 can be made of gallium arsenide, silicon, silicon carbide, aluminum oxide, indium phosphide, gallium phosphide, aluminum nitride or gallium nitride, etc. Optical substrate or light-absorbing substrate; grow n-type semiconductor layer 2 (such as n-GaN, n-AlGaInP), multi-quantum well active layer 3 (such as InGaN, AlGaInP), and p-type semiconductor layer sequentially by metalorganic chemical vapor phase epitaxy 4 (such as p-GaN, p-AlGaInP) and other layers to form a light-emitting diode epitaxial structure, wherein the n-type semiconductor layer and the p-type semiconductor layer can be used as confinement layers. Utilize the novel holographic exposure system structure of Fig. 2 again, two incident lights are directly hit on the surface of the whole structure of the light-emitting diode to form interference fringes, when the wavelength of the selected laser light source is less than the corresponding wavelength of the multi-quantum well active layer structure 3 (λ _laser <λ _QW ), the two incident light interferences can achieve light intensity changes with a period of 200nm-1000nm, and then by controlling the light intensity and the length of incident light time, different degrees of energy gap changes and refractive index changes can be controlled . Then use the rotator (Rotator) B to determine the angle Ψ of the internal diffusion effect of the two quantum wells (can be between 20-90 degrees) according to the requirements. Also by controlling the light intensity, the area where the internal diffusion effect of the quantum well is repeated (intersection) ) has a large energy difference, which in turn produces a change in the refractive index. The amount of change has a two-dimensional spatial periodicity, and the two-dimensional period does not need to be consistent, that is, a photonic crystal light-emitting element (as shown in FIG. 6b ) is formed. A current spreading layer 7 is then formed on the p-type semiconductor layer, and after the current spreading layer is etched down to the n-type semiconductor layer, a p-type electrode 9 and an n-type electrode 8 are respectively formed on the current spreading layer and the n-type semiconductor layer , that is, a photonic crystal light-emitting diode element is formed, as shown in FIG. 8 .

Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Those skilled in the art may make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the present invention The scope of protection shall prevail as defined by the appended claims.

Claims (9)

1. light-emitting component comprises:

Substrate; And

The semiconductor epitaxial structure is positioned on this substrate, wherein this semiconductor epitaxial structure has mqw active layer, and this mqw active layer is included in one dimension or two-dimensional space has the periodically photon crystal structure of change in dielectric constant, and wherein this photon crystal structure is to interfere in this mqw active layer in conjunction with the twice incident light by the basis with the holography exposure technique to cause the diffusion inside effect to be formed.

2. light-emitting component as claimed in claim 1, wherein this semiconductor epitaxial structure also comprises:

The first electrical semiconductor layer is formed between this substrate and this mqw active layer; And

The second electrical semiconductor layer is formed on this mqw active layer, and this first electrical semiconductor layer and/or this second electrical semiconductor layer can be used as limiting layer.

3. light-emitting component as claimed in claim 1, wherein this change in dielectric constant has the one-dimensional space periodically, and its scope is 200nm-1000nm.

4. light-emitting component as claimed in claim 1, wherein this change in dielectric constant has two-dimensional space periodically, and its scope is 200nm-1000nm, and cycle that should two dimension does not need unanimity.

5. light-emitting component as claimed in claim 1, wherein the optical maser wavelength of this holography exposure technique needs less than light wavelength that this mqw active layer produces.

6. light-emitting component as claimed in claim 2, wherein this lambda1-wavelength is less than this first semiconductor layer and/or the pairing wavelength of this second semiconductor layer.

7. light-emitting component as claimed in claim 6, wherein this lambda1-wavelength is between this first semiconductor layer and/or this second semiconductor layer and the pairing wavelength of this quantum well.

8. light-emitting component as claimed in claim 1, wherein this photon crystal structure is interfered the secondary quantum well diffusion inside effect that causes through secondary twice incident light, and the angle of this secondary quantum well diffusion inside effect can form two-dimensional photon crystal structure between the 20-90 degree.

9. light-emitting component as claimed in claim 1, wherein this photon crystal structure has one dimension or the variation of the periodic material composition of two-dimensional space.

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