TWI401826B - Light emitting device and method for enhancing light extraction thereof - Google Patents

Description

Light-emitting device with gain and light and method thereof

The invention relates to a method for improving the light emission of a light-emitting device, in particular to a method for controlling the lightening of a light-emitting device by forming a controllable roughening oxide layer (such as a zinc oxide layer) on the light-emitting device.

Since the development of integrated circuits (ICs) to nano-scales, the application of nano-components has become increasingly popular, especially for short-wavelength illuminators such as Laser Diodes (LDs) and Light Emitting Diodes (LEDs) have become mainstream. In the development of short-wavelength light-emitting devices, III-V compound semiconductors are the most commonly used materials for the manufacture of LEDs. However, due to the development of new system materials, II-VI compound semiconductors have received renewed attention. In fact, zinc oxide (ZnO) has the advantages of low cost and easy synthesis, and its energy gap and crystal structure are similar to those of GaN. Therefore, research on ZnO has become a hot topic, especially the development of ZnO nanopillars. application.

The direct band-gap of ZnO is 3.37 eV, which is higher than other high direct energy gap semiconductor materials. In addition, ZnO has a higher excitation binding energy (the excitation bonding energy of gallium nitride is about 20 meV, and the excitation bonding energy of ZnO is about 60 meV, which is much higher than that of gallium nitride). Therefore, at room temperature, its luminous efficiency is higher than other materials. In recent years, many ZnO research reports indicate that its good luminescence efficiency can be applied to short-wavelength components and laser diodes. Since data reading can be improved by ultraviolet (UV) lasers, ZnO has great potential for UV laser sources.

Another major development direction of ZnO is a one-dimensional nanocolumn (nanowire). Scientists can successfully generate highly aligned arrays of nanopillars. The UV laser can be excited from the nano column by photoluminescence. Although UV lasers can be commercialized in many ways, there are still two problems to be solved in how to enhance the light output and control the light escape angle of the nano column. Otherwise, the luminous efficiency will be greatly affected.

In view of the above problems, the present invention proposes a solution to gain light emission from a light-emitting device.

In view of the prior art limitations to the above problems, it is an object of the present invention to provide a method of gaining light output from a light-emitting device by forming a controllable rough oxide layer (e.g., a zinc oxide layer) on the light-emitting device.

According to one aspect of the present invention, a method for improving light emission from a light emitting device includes the steps of: a) providing a wiring layer on the light emitting device; b) providing a protective layer on the wiring layer; c) forming an array of pore penetrating protective layers and a layer of the layer; and d) an oxide layer formed on the layer, having a plurality of pillars each formed in one of the pores. The shape of the cylinder can be controlled by adjusting the N ₂ /H ₂ concentration ratio of the atmosphere, the reaction temperature and time, thus changing the shape of the cylinder and the light escape angle.

According to the concept of the invention, the oxide layer comprises zinc oxide (ZnO), cerium oxide (SiO ₂ ), titanium dioxide (TiO ₂ ) or aluminum oxide (Al ₂ O ₃ ). .

In accordance with the teachings of the present invention, the oxide layer is formed by hydrothermal treatment, sol-gel method, electroplating, thermal evaporation, chemical vapor deposition (CVD), or molecular beam epitaxy (MBE).

According to the concept of the present invention, the layout layer includes indium tin oxide (ITO), nickel/gold (Ni/Au), nickel oxide/gold (NiO/Au), P-type zinc oxide (p-ZnO), or zinc oxide (ZnO). ).

According to the concept of the invention, the protective layer comprises a photoresist material or a dielectric material.

According to the concept of the invention, the atmosphere temperature is above 200 °C.

According to the concept of the invention, the atmosphere comprises nitrogen, hydrogen, or a mixture thereof.

According to the concept of the invention, the cylinder has a nanostructure or a microstructure.

According to the concept of the invention, the cylinder is hexagonal or truncated hexagonal.

According to the concept of the invention, the diameter of the lower surface of the cylinder is between 100 nm (nano) and several [mu]m (micrometer).

In accordance with the teachings of the present invention, the voids are formed by a wet etch process, a dry etch process, a photolithography process and an exposure development process, a laser dicing process, or an electron beam writing process.

According to another aspect of the present invention, a light-emitting device having a light-emitting light includes a light-emitting substrate; a wiring layer provided on the light-emitting substrate; an array of pores formed in the wiring layer; and a protection layer disposed on the wiring layer having the exposed pores a layer; and an oxide layer formed on the wiring layer, having a plurality of pillars each formed in one of the pores. The shape of the cylinder can be controlled by adjusting the atmosphere N ₂ /H ₂ concentration ratio, reaction temperature and time, thus changing the shape of the cylinder and the light escape angle.

According to the concept of the invention, the oxide layer comprises zinc oxide (ZnO), cerium oxide (SiO ₂ ), titanium dioxide (TiO ₂ ) or aluminum oxide (Al ₂ O ₃ ).

According to the concept of the present invention, the oxide layer is formed by hydrothermal treatment, sol-gel method, electroplating, thermal evaporation, chemical vapor deposition (CVD), or molecular beam epitaxy (MBE).

According to the concept of the invention, the routing layer comprises ITO, Ni/Au, NiO/Au, p-ZnO, or ZnO.

According to the concept of the invention, the protective layer comprises a photoresist material or a dielectric material.

According to the concept of the invention, the atmosphere temperature is above 200 °C.

According to the concept of the invention, the atmosphere comprises nitrogen, hydrogen, or a mixture thereof.

According to the concept of the invention, the cylinder has a nanostructure or a microstructure.

According to the concept of the invention, the cylinder is hexagonal tapered or truncated hexagonal cone.

According to the concept of the invention, the diameter of the lower surface of the cylinder is between 100 nm (nano) and several [mu]m (micrometer).

In accordance with the teachings of the present invention, the voids are formed by a wet etch process, a dry etch process, a photolithography process and an exposure development process, a laser dicing process, or an electron beam writing process.

The invention will be more specifically disclosed in the following examples. It should be noted that the following description of the embodiments of the present invention is for the purpose of description and drawings only, and the invention itself is not limited to the disclosed forms and styles.

1 is a flow chart of a preferred embodiment of the present invention, showing a method of emitting light from a gain illuminating device by forming an oxide layer having a controllable roughness on the illuminating device. Figure 2 is a 3D perspective view of the present invention showing the relative positions of the various components of the present invention. Please refer to FIG. 1 and FIG. 2 . The method for improving the light output of the light-emitting device of the present invention comprises the following steps. First, the light-emitting device 102 is provided with a surface layer 104 formed on its upper surface (as shown in step S101). In the present embodiment, the surface layer 104 is made of P-type gallium nitride (p-GaN). However, the surface layer 104 of the present invention is not limited to p-GaN, and may be composed of p-AlGaN, p-InGaN, p-GaN/InGaN SLs, p-AlGaN/GaN SLs, p-AlInGaN, p-InAlGaN/InAlGaN SLs, n- (In) (Al) GaN, n-InGaN, ITO, p-ZnO, ZnO, Ni/Au, or NiO/Au. In other words, the surface layer 104 is not limited to the P-type or N-type conductivity type.

The light-emitting device 102 in this embodiment is a gallium nitride light-emitting diode whose energy band gap corresponds to a wavelength of 200 nm to 750 nm.

A routing layer 106 is then provided on the surface layer 104 of the illumination device 102 (as in step S102). The wiring layer 106 may be made of indium tin oxide (ITO), nickel/gold (Ni/Au), nickel oxide/gold (NiO/Au), P-type zinc oxide (p-ZnO), or zinc oxide (ZnO).

A protective layer 107 is disposed on the routing layer 106 (step S103). Please refer to FIG. 3, which is a cross-sectional view taken along line A-A' of FIG. 2. The wet etching process, the dry etching process, the photolithography process and the exposure development process, the laser cutting process, or the electron beam writing process are performed to form an array of the voids 109 penetrating the protective layer 107 and the routing layer 106 (step S104). ). When a photolithographic process is used, the protective layer 107 is made of a photoresist material, and when an etching process is used, the protective layer 107 is made of a photoresist material or a dielectric material.

An oxide layer having a plurality of pillars 108 is formed in the routing layer 106, and the pillars 108 are thus formed in one of the apertures 109. The protective layer 107 serves to position the cylinder 108 to the aperture 109 and to prevent the cylinder 108 from being generated outside of the aperture 109.

Controlling the temperature and concentration of the atmosphere can adjust the shape of the cylinder 108 such that the light escape angle of the cylinder can be varied, as in steps S105 through S106.

The oxide layer may be made of zinc oxide (ZnO), cerium oxide (SiO ₂ ), titanium dioxide (TiO ₂ ) or aluminum oxide (Al ₂ O ₃ ). In this embodiment, the oxide layer is made of ZnO.

In this embodiment, the oxide layer is formed by hydrothermal treatment. First, the light-emitting device including the wiring layer was washed with acetone, methanol, and deionized water for about 5 minutes each. The illuminating device and the laying layer were blown dry with a nitrogen lance. Next, a seed layer of ZnO is formed on the wiring layer to increase adhesion. The illuminating device, the routing layer, and the seed layer are collectively referred to as a mediator.

The seed layer of ZnO is prepared by dissolving zinc acetate (Zn(CH ₃ COO) ₂ ‧H ₂ O, zinc acetate) in ethylene glycol methyl ether (CH ₃ O(CH ₂ ) ₂ OH, 2-methoxyethanol). The concentration of both was 0.5 M, and then the mixed solution was stirred at a heating temperature of 65 ° C for two hours to obtain a transparent colloidal solution. The transparent colloidal solution is then spin coated onto the upper surface of the laid layer. Next, at a temperature of 130 ° C, the wiring layer on which the transparent colloidal solution was placed was subjected to thermal annealing for 60 minutes to obtain a zinc oxide seed layer. In the present embodiment, the ZnO seed layer is used as a ZnO particle to form a ZnO layer.

The seed layer is not limited to being made of zinc oxide, and may be made of gold (Au), silver (Ag), tin (Sn), or cobalt (Co). The oxide layer can be formed randomly or sequentially.

After the seed layer is formed, the medium is placed face down, placed in a purity of 99.5% of hexamethylenetetramine (C ₆ H ₁₂ N ₄ , HMT, hexamethylenetetramine) and 98% pure zinc nitrate (Zn(NO ₃ ) _In the growth solution of ₂ ‧6H ₂ O, zinc nitrate hexahydrate), the concentration of both was 0.5M. It was then heated in a dryer at a low temperature of 90 ° C for about 3 hours. After heating, it was taken out and rinsed with deionized water. A zinc oxide layer having a plurality of columns can thus be obtained. The height, growth rate, and size of the ZnO cylinder can be controlled by adjusting the temperature, concentration, and growth time.

When hydrothermal treatment, the formation of ZnO is based on the following molecular formula:

In the above deposition mechanism, once the concentrations of zinc ions and hydroxide ions are saturated, ZnO starts to form on the seed layer. Due to the anisotropy of atomic bonding, when atoms grow on the nucleus, they tend to migrate to low energy, causing a certain energy to grow in a direction of asymmetry in a particular direction. Thus a column/linear array structure is formed.

This embodiment uses hydrothermal treatment, but the invention is not limited to the use of hydrothermal treatment, but also thermal evaporation, sol-gel method, chemical vapor deposition (chemical vapor deposition) , CVD), or molecular beam epitaxy (MBE).

Further, in the present embodiment, the seed layer is disposed on the GaN substrate by spin coating, and dip coating, evaporation, sputtering, or atomic layer may be used. Atomic layer deposition, electrochemical deposition, pulse laser deposition, metal-organic chemical vapor deposition, or thermal annealing.

The atmosphere may comprise nitrogen, hydrogen, or a mixture thereof. In addition, the temperature of the controllable coarsening of the ZnO cylinder is higher than 200 °C.

Under the above-described atmospheric conditions, the cylinder 108 may appear as a hexagonal pyramid or a truncated hexagonal cone having a size between nanometers and several micrometers. The diameter of the lower surface of the cylinder 108 is between 100 nm (nano) and several μm (micrometer).

Referring to FIG. 4 , the pillar 108 of the ZnO layer is formed in the aperture 109 of the routing layer 106 . The columns 108 each have a hexagonal cross section and a Wurtzite Structure, as shown in FIG. In the present invention, it is presented as a hexagonal cylinder. Depending on the structure of the cylinder 108, the light beam is emitted from the illumination device 102 in a particular direction.

Figure 6 illustrates the formation of columns 108 of various shapes under ambient conditions of varying temperatures and concentrations. For example, the cylinder 108 of FIG. 6A is hexagonal tapered, formed at a ratio of nitrogen to hydrogen concentration less than that of FIG. 6C, and the cylinder of FIG. 6C is shown as a truncated hexagonal pyramid. The column 108 of Figure 6A can also be formed at a temperature above that of Figure 6C. Therefore, the roughening of the light-emitting device can be controlled by changing the pyramid shape (sharpness) of the oxide layer cylinder 108.

Please refer to FIG. 7 and FIG. 8 , which illustrate different optical paths of the hexagonal column and the hexagonal cone. In contrast to Figure 7, the hexagonal cone of Figure 8 apparently produces refraction and increases the light escape angle, thus changing the direction of the light. Therefore, the light output of the light-emitting device can be greatly increased, and the light escape angle can also be controlled by the present invention.

Although the present invention has been disclosed above by way of example, it is not intended to limit the invention. To the contrary, the scope of the invention is defined by the scope of the appended claims. quasi.

S101~S106. . . step

102. . . Illuminating device

104. . . surface layer

106. . . Layout layer

107. . . The protective layer

108. . . Cylinder

109. . . Porosity

1 is a flow chart of a preferred embodiment of the present invention.

Figure 2 is a 3D perspective view of the present invention.

Figure 3 is a cross-sectional view taken along line A-A' of Figure 2 to illustrate the formation of voids.

Figure 4 is a cross-sectional view taken along line A-A' of Figure 2 to illustrate the formation of the cylinder.

Figure 5 is an enlarged view of the cylinder.

Figure 6 illustrates the structure of the cylinder formed in different environments.

Figure 7 illustrates the optical path in a hexagonal cylindrical cylinder.

Figure 8 illustrates the optical path in a hexagonal tapered cylinder.

S101~S106. . . step

Claims (19)

A method for improving light emission of a light emitting device, comprising the steps of: providing a laying layer on the light emitting device; providing a protective layer on the laying layer; forming an array of pore penetrating protective layer and laying layer; and forming an oxide layer on the laying layer, There are a plurality of cylinders each formed in one of the pores; wherein the shape of the cylinder is obtained by controlling the temperature of the atmosphere to be higher than 200 ° C, wherein the atmosphere includes nitrogen, hydrogen, or a mixture thereof. The method of claim 1, wherein the oxide layer comprises zinc oxide (ZnO), cerium oxide (SiO ₂ ), titanium dioxide (TiO ₂ ) or aluminum oxide (Al ₂ O ₃ ). The method of claim 1, wherein the oxide layer is formed by hydrothermal treatment, sol-gel method, electroplating, thermal evaporation, chemical vapor deposition (CVD), or molecular beam epitaxy (MBE). . The method of claim 1, wherein the wiring layer comprises indium tin oxide (ITO), nickel/gold (Ni/Au), nickel oxide/gold (NiO/Au), and p-type zinc oxide (p-ZnO). Or zinc oxide (ZnO). The method of claim 1, wherein the protective layer comprises a photoresist material or a dielectric material. The method of claim 1, wherein the cylinder has a nanostructure or a microstructure. The method of claim 1, wherein the cylinder has a hexagonal cone shape or a truncated hexagonal cone shape. The method of claim 1, wherein the lower surface of the cylinder is straight The diameter is between 100 nm (nano) and several μm (micron). The method of claim 1, wherein the pores are formed by a wet etching process, a dry etching process, a photolithography process and an exposure development process, a laser cutting process, or an electron beam writing process. A light-emitting device having a light-emitting light, comprising: a light-emitting substrate; a wiring layer provided on the light-emitting substrate; an array of pores formed in the wiring layer; a protective layer disposed on the wiring layer having the exposed pores; and being formed on the wiring layer The upper oxide layer has a plurality of pillars each formed in one of the pores; wherein the pillar shape may be a hexagonal cone shape or a truncated hexagonal cone shape. A light-emitting device according to claim 10, wherein the oxide layer comprises zinc oxide (ZnO), cerium oxide (SiO ₂ ), titanium oxide (TiO ₂ ) or aluminum oxide (Al ₂ O ₃ ). The illuminating device of claim 10, wherein the oxide layer is formed by hydrothermal treatment, sol-gel method, electroplating, thermal evaporation, chemical vapor deposition (CVD), or molecular beam epitaxy (MBE). . The illuminating device of claim 10, wherein the laying layer comprises indium tin oxide (ITO), nickel/gold (Ni/Au), nickel oxide/gold (NiO/Au), and p-type zinc oxide (p-ZnO). Or zinc oxide (ZnO). The illuminating device of claim 10, wherein the protective layer comprises a photoresist material or a dielectric material. The illuminating device of claim 10, wherein the temperature of the atmosphere Above 200 °C. A light-emitting device according to claim 10, wherein the atmosphere comprises nitrogen, hydrogen, or a mixture thereof. The illuminating device of claim 10, wherein the cylinder has a nanostructure or a microstructure. The illuminating device of claim 10, wherein the diameter of the lower surface of the cylinder is between 100 nm (nano) and several μm (micrometer). The illuminating device of claim 10, wherein the void is formed by a wet etching process, a dry etching process, a photolithography process and an exposure development process, a laser cutting process, or an electron beam writing process.