CN101685844A - GaN-based Single chip white light emitting diode epitaxial material - Google Patents

Abstract

The invention relates to a GaN-based single-chip white light-emitting diode epitaxial material, which includes a substrate, an initial growth layer grown sequentially on the substrate, an intrinsic GaN buffer layer, an n-type GaN layer, a stress relaxation layer, and an InGaN multi-quantum Well structure light-emitting layer, p-type AlGaN interlayer and p-type GaN layer; the stress relaxation layer is an InGaN/GaN superlattice stress modulation layer, which is composed of alternately grown InGaN layers and GaN layers, wherein the alternately grown InGaN layers and GaN The growth cycle of the layer is 6-500, and the corresponding thickness is 10nm-3μm; the In composition in the InGaN layer is in the range of 1%-35%. In the present invention, a stress-relaxed InGaN/GaN superlattice stress modulation layer is added between the N-type GaN layer and the quantum well light-emitting layer to enhance the segregation effect of In and form InGaN quantum dots with different components. These quantum dots emit light of different wavelengths to achieve white light emission; fundamentally reduce the cost of white light emitting diodes, increase light emission efficiency and utilization efficiency, and improve the overall performance of white light emitting diodes.

Description

Epitaxial materials for GaN-based single-chip white light-emitting diodes

technical field

The invention relates to a white light emitting diode epitaxial material, in particular to an epitaxial material for a white light GaN-based single-chip light emitting diode chip that does not require phosphor powder conversion.

Background technique

As a white light source, white light-emitting diodes have many advantages such as high luminous efficiency, short response time, and long life. These advantages determine that it will replace the existing white light source. At present, there are three kinds of manufacturing methods for white light-emitting diodes that are generally accepted: (1) three red, green and blue light-emitting diodes that are separately produced or integrated in a single chip emit light at the same time, thereby mixing white light, (2) The red, green and blue three-color mixed phosphor powder wrapped in the outer layer is excited by the ultraviolet or purple light-emitting diode as the light source, and the three-color phosphor emits and mixes to obtain white light. (3) The blue light-emitting diode is used as the light source to partially excite the outer package The yellow light phosphor powder emits yellow light, and the blue light emitted by the internal light-emitting diode and the yellow light obtained by exciting the phosphor powder are mixed to obtain white light.

Among them, the production method (1) has not been applied due to cost and technical reasons; the production method (2) is relatively simple and the most promising white light-emitting diode production method, but because no suitable ultraviolet radiation resistance has been found so far. According to the encapsulation resin and the lack of efficient red phosphors, it has not been widely used; method (3) is a white light-emitting diode production method that has been commercialized at present, and the same lack of suitable red phosphors makes the white light-emitting diodes The luminous quality is limited. The white light spectrum obtained by mixing two colors of light is relatively simple, the luminous color temperature is high and the color rendering index is low. Although method (3) has been commercialized and the color rendering index and color temperature have been effectively improved after years of exploration, its essence is the core problem of phosphor conversion, that is, the process of phosphor converting blue light into yellow light. , will inevitably lead to the Stokes frequency shift and cause the problem of low luminous efficiency, which still restricts the further development of this method.

Previously, the applicant applied for the patent of GaN white light-emitting diode without phosphor powder conversion (patent application number: 200610065103.1). This patent uses the InGaN stress relaxation layer as the stress modulation template of the quantum well light-emitting layer, so that In the InGaN quantum well, due to the effect of the stress template, the segregation effect of In is enhanced to form InGaN quantum dots with different In compositions or different sizes. These quantum dots emit a mixture of different wavelengths of light (broad-spectrum luminescence) to achieve white light emission. However, the GaN-based white light-emitting diode without phosphor powder conversion still has the defect that the white light luminous efficiency is not high enough, and it cannot meet the requirements for practical use.

Contents of the invention

The object of the present invention is: in order to improve the luminous efficiency of the existing single-chip white light emitting diode without phosphor powder conversion, thereby providing a kind of relaxation by using the relaxed InGaN/GaN superlattice structure instead of the existing single-layer InGaN layer, GaN-based single-chip white light-emitting diode epitaxial material, the material can realize stress modulation, and can significantly reduce the dislocation in the relaxation layer with the help of the unique function of the superlattice structure to reduce dislocations, which will be used for the follow-up The epitaxial quantum well luminescent central layer provides a high-quality stress-modulated template, which can effectively improve the luminous efficiency of single-chip white light.

The purpose of the present invention is achieved like this:

A GaN-based single-chip white light-emitting diode epitaxial material provided by the present invention includes a substrate, and an initial growth layer, an intrinsic GaN buffer layer, an n-type GaN layer, and a stress relaxation layer grown sequentially on the substrate. layer, an InGaN multi-quantum structure light-emitting layer, a p-type AlGaN interlayer and a p-type GaN layer; it is characterized in that: the stress relaxation layer is composed of alternately grown InGaN and GaN superlattices, wherein the superlattice stress modulation layer The thickness is 10nm-3μm, and the cycle of the alternate growth of the InGaN/GaN layer is 6-500 cycles; the In composition in the InGaN layer is in the range of 1% to 35% (see Figure 1 for the detailed structure ), the stress of the superlattice is relaxed.

A GaN-based single-chip white light-emitting diode epitaxial material provided by the present invention includes a substrate, and an initial growth layer, an intrinsic GaN buffer layer, an n-type GaN layer, and a stress relaxation layer grown sequentially on the substrate. layer, an InGaN multi-quantum structure light-emitting layer, a p-type AlGaN interlayer, and a p-type GaN layer; it is characterized in that: the stress relaxation layer is a superlattice stress modulation layer, and the superlattice stress modulation layer is formed by alternately growing In _x Ga _1-x N layer and In _y Ga _1-y N layer, wherein the thickness of the superlattice stress modulation layer is 10nm-3μm, and the In _x Ga _1-x N/In _y Ga _1-y N alternate The period of the growth layer is 6-500; the In composition x and y of the InGaN satisfy x>y, and x is regulated in the range of 1% to 35%, y is regulated in the range of 0 to 35%, and the superlattice The stress is relaxed.

In the above technical scheme, the InGaN in the _InGaN /GaN superlattice relaxation layer is _{InxAlyGa1 -xyN} ;

The GaN in the InGaN/GaN superlattice relaxation layer is In _y Al _z Ga _1-yz N or Al _x Ga _1-x N.

In the above technical scheme, the substrate is a sapphire substrate, a SiC substrate or a silicon substrate;

The initial growth layer is an AlN layer or a GaN layer; its thickness is 20nm-2μm;

The intrinsic GaN layer is a GaN layer, an AlN layer, an AlGaN layer, an InGaN layer, an InAlN layer, an InAlGaN layer, or a combination of these alloys and is epitaxial transition layer on a heterogeneous substrate; its thickness is 50nm-2μm ;

The n-type GaN layer is a GaN layer, an AlN layer, an AlGaN layer, an InGaN layer, an InAlN layer, an InAlGaN layer, or an n-type ohmic contact layer of a combination of these alloys; its thickness is 50nm-3μm;

The InGaN multi-quantum structure light-emitting layer is the active layer of a light-emitting diode composed of a barrier layer In _y Ga _1-y N and a quantum well layer In _x Ga _1-x N, where y<x, 0.1<x< 0.3, 0<y<0.15; the quantum well layer In _x Ga _1-x N is composed of quantum dots and a wetting layer or two quantum structures of different components produced by phase separation and condensation; the barrier layer The doping concentration of In _y Ga _1-y N and the quantum well layer In _x Ga _1-x N layer is 0~1×10 ¹⁸ /cm ³ , the thickness of the barrier layer is 5-15nm, and the thickness of the quantum well layer is 2-5nm ; The period number of the quantum well is 1-20;

The p-type AlGaN interlayer is an Al _m Ga _1-m N interlayer, wherein m is 0-0.2; its thickness is 5nm-1μm;

The p-type GaN layer is a GaN layer, an InAlN layer, an AlGaN layer, an InAlGaN layer, or a combination of these alloys to form a p-type ohmic contact layer. Its thickness is 10nm-1μm.

The growth method of the GaN-based single-chip white light emitting diode epitaxial material proposed by the present invention can be realized by metal-organic chemical vapor phase epitaxy or molecular beam epitaxy on sapphire, Si or SiC substrates.

This GaN-based white light emitting diode without phosphor powder conversion avoids the limitations of the aforementioned three white light technologies. The process technology is simple, compatible with conventional blue light emitting diode technology, and the cost is low, which will help promote semiconductor lighting into the family early. application.

Based on the patented technology of GaN-based white light-emitting diodes without phosphor conversion, the present invention replaces the existing single-layer InGaN relaxation layer with a relaxed InGaN/GaN superlattice structure, so that the stress can be modulated at the same time. It can also effectively reduce dislocations in the material, thereby effectively improving the luminous efficiency of single-chip white light.

Compared with the prior art, the advantages of the light-emitting diode prepared by using the GaN-based single-chip white light-emitting diode epitaxial structure material of the present invention are:

1. By using the InGaN/GaN superlattice stress modulation layer, the InGaN luminescent centers with different In components in the light-emitting layer emit light of different wavelengths due to the enhanced phase separation of In and emit light of different wavelengths. The method of mixing these multi-wavelength light into white light The purpose of emitting white light from a single chip is realized, the manufacturing process and process of conventional white light emitting diodes containing phosphor are simplified, and the cost of white light emitting diodes is reduced. At the same time, since there is no phosphor powder conversion, there is no Stokes frequency shift effect, which improves the light utilization efficiency of the light emitting diode.

2. By using the InGaN/GaN superlattice stress modulation layer instead of the relaxed InGaN layer, on the one hand, the single-layer InGaN stress modulation can be achieved, and the dislocation bending or dislocation can be realized through the alternating action of the superlattice multilayer interface. Merge, so as to achieve the purpose of effectively filtering dislocations. Therefore, it is beneficial to reduce the dislocation in the light-emitting layer, improve the light-emitting efficiency of the light-emitting layer, and further improve and enhance the performance of the single-chip white light-emitting device.

3. The present invention fundamentally reduces the cost of white light-emitting diodes without increasing the complexity of epitaxial structure material preparation and device process preparation, increases light emission efficiency and utilization efficiency, and overcomes conventional phosphor conversion to obtain white light-emitting diodes The disadvantages, improve the overall performance of white light emitting diodes.

In summary, the core content of the present invention is based on the GaN white light emitting diode patent without phosphor powder conversion (patent application number: 200610065103.1), by replacing the InGaN relaxation layer with an InGaN/GaN superlattice, and simultaneously realizing The dual effects of filtering dislocations and stress modulation can further improve the single-chip white light emission performance. Figure 2 shows a single From the luminous characteristic curve of the chip white light emitting diode, it can be seen that the white light luminous intensity of the relaxed superlattice stress modulation layer is stronger.

Description of drawings

Fig. 1 is a schematic diagram of the material structure of a single-chip white light emitting diode containing an InGaN/GaN superlattice stress modulation layer.

Fig. 2 is the emission spectrum of a single-chip white light-emitting diode using an InGaN/GaN superlattice stress modulation layer and a single-layer InGaN relaxation layer, respectively.

Detailed ways

The structure of the GaN-based single-chip white light emitting diode epitaxial material of the present invention will be described in detail below through the growth method of the material. The epitaxial material structure of the GaN-based single-chip white light emitting diode in the embodiment, and the other epitaxial structure layers except the relaxed stress modulation layer adopt the disclosed structure of the GaN-based blue light emitting diode.

Example 1

Referring to Fig. 1, a GaN-based single-chip white light-emitting diode epitaxial material of the present invention is produced, and its structure is as follows:

Using sapphire as the substrate 1, a 20nm thick GaN initial growth layer 2, a 200nm intrinsic GaN layer 3, and a 1 μm thick n-type GaN layer 4 (doped Concentration 5×10 ¹⁸ cm ^-3 ), 20 cycles of 10nm thick (referring to the thickness of In _0.1 Ga _0.9 N single layer) In _0.1 Ga _0.9 N/10nm thick GaN superlattice stress modulation layer 5, InGaN multi-quantum Structural light-emitting layer 6 (5 periods of multiple quantum wells composed of barrier layer In _0.05 Ga _0.95 N and quantum well layer In _0.15 Ga _0.85 N, wherein the thickness of the barrier layer In _0.05 Ga _0.95 N is 10nm, and the quantum well layer In _0.15 Ga _0.85 N thickness is 3nm), 100nm thick p-type Al _0.2 Ga _0.8 N interlayer 7, 100nm thick p-type GaN layer 8 (doping concentration 3×10 ¹⁷ cm ^-3 ), to obtain GaN-based single-chip white light Light-emitting diode epitaxial structure material (shown in Figure 1). The electroluminescence spectrum of the structure after the device process is shown in FIG. 2 .

Example 2

Referring to FIG. 1, a GaN-based single-chip white light-emitting diode epitaxial material of the present invention is produced: a 0.4 mm thick SiC is used as a substrate 1, and a 100 nm thick SiC is sequentially grown on it using a metal organic chemical vapor deposition technique (MOCVD). AlN initial growth layer 2, 0.3μm thick intrinsic GaN layer 3, 1μm thick n-type GaN layer 4, 150nm thick 5nmIn _0.15 Ga _0.85 N/10nm thick In _0.05 Ga _0.95 N superlattice stress modulation Layer 5, InGaN multi-quantum structure light-emitting layer 6 (four periods of multi-quantum wells composed of barrier layer GaN and quantum well layer In _0.15 Ga _0.85 N, wherein the thickness of the barrier layer GaN is 12nm, and the quantum well layer In _0.15 The thickness of Ga _0.85 N is 3nm, the doping concentration of the barrier layer GaN is 1×10 ¹⁸ /cm ³ , the doping concentration of the quantum well layer InxGa1-xN layer is 0), and the thickness of 50nm p-type Al _0.2 Ga _0.8 The N interlayer 7 and the P-type GaN layer 8 with a thickness of 500nm are used to obtain epitaxial materials for white light GaN light-emitting diodes that do not require phosphor powder conversion, as shown in FIG. 1 .

Example 3

Referring to Fig. 1, a GaN-based single-chip white light emitting diode epitaxial material of the present invention is produced: a 0.3 mm thick silicon substrate is used as the substrate 1, and a 200 nm thick AlN initial layer is sequentially grown on it by molecular beam epitaxy (MBE). Growth layer 2, 0.5 μm thick intrinsic GaN layer 3, 0.5 μm thick n-type GaN layer 4, 15 periods of 1nm In _0.3 Ga _0.7 N/8nm In _0.05 Al _0.02 Ga _0.93 N superlattice stress modulation layer 5 , InGaN multi-quantum structure light-emitting layer 6 (four periods of multi-quantum wells composed of barrier layer GaN and quantum well layer In _0.15 Ga _0.85 N, wherein the thickness of the barrier layer GaN is 10nm, and the quantum well layer In _0.15 Ga _0.85 The thickness of N is 3 nm, the doping concentration of GaN in the barrier layer is 1×10 ¹⁷ /cm ³ , the doping concentration of the quantum well layer In _x Ga _1-x N layer is 2×10 ¹⁷ /cm ³ ), A 100nm-thick p-type Al _0.2 Ga _0.8 N interlayer 7 and a 300nm-thick p-type GaN layer 8 were used to obtain the GaN-based single-chip white light emitting diode epitaxial structure material, as shown in FIG. 1 .

Example 4

Referring to FIG. 1 , a GaN-based single-chip white light-emitting diode epitaxial material of the present invention is produced: a similar structure as in Example 2 is adopted except that the superlattice stress modulation layer 5 is modified. The changed structure of the superlattice stress modulation layer 5 is: 6 periods of 10nm In _0.2 Ga _0.8 N/10nm GaN superlattice stress modulation layers. The structure of the white light emitting diode containing the stress modulation layer is shown in Figure 1, and the epitaxial material of the white light GaN light emitting diode without phosphor conversion can be obtained.

Example 5

Referring to FIG. 1 , a GaN-based single-chip white light-emitting diode epitaxial material of the present invention is produced: a similar structure as in Example 3 is adopted except that the superlattice stress modulation layer 5 is modified. The changed structure of the superlattice stress modulation layer 5 is: 10nm In _0.01 Ga _0.99 N/1nmGaN superlattice stress modulation layer with 150 cycles. The structure of the white light emitting diode containing the stress modulation layer is shown in Figure 1, and the white light GaN light emitting diode epitaxial material without phosphor conversion can be obtained.

Example 6

Referring to FIG. 1 , a GaN-based single-chip white light-emitting diode epitaxial material of the present invention is produced: a similar structure as in Embodiment 1 is adopted except that the superlattice stress modulation layer 5 is modified. The changed structure of the superlattice stress modulation layer 5 is: 40 cycles of 5nm In _0.08 Al _0.02 Ga _0.9 N/2nmAl _0.01 Ga _0.98 N superlattice stress modulation layers. The structure of the white light emitting diode containing the stress modulation layer is shown in Figure 1, and the epitaxial material of the white light GaN light emitting diode without phosphor conversion can be obtained.

Example 7

Referring to FIG. 1 , a GaN-based single-chip white light-emitting diode epitaxial material of the present invention is produced: a similar structure as in Embodiment 1 is adopted except that the superlattice stress modulation layer 5 is modified. The changed structure of the superlattice stress modulation layer 5 is: 400 periods of 2nm thick In _0.02 Ga _0.98 N/3nmGaN superlattice stress modulation layer. The structure of the white light emitting diode containing the stress modulation layer is shown in Figure 1, and the epitaxial material of the white light GaN light emitting diode without phosphor conversion can be obtained.

The composition of the superlattice stress modulation layer in the GaN-based single-chip white light emitting diode epitaxial material structure proposed in the above embodiments, that is, the two-layer material of the superlattice can be In _x Ga _1-x N and In _y Ga _1-y Composed of N superlattice, wherein the components x and y of In satisfy x>y, and x is regulated in the range of 1% to 35%, and y is regulated in the range of 0 to 35%; the superlattice stress modulation layer The thickness of the InGaN/GaN layer is 10nm-3μm, and the cycle of the alternate growth of the InGaN/GaN layer is 6-500 cycles; the stress of the superlattice is relaxed.

The superlattice stress modulation layer in the GaN-based single-chip white light emitting diode epitaxial material structure proposed in the above embodiments is characterized in that the two layers of materials InGaN and GaN that make up the superlattice can be expanded according to the principles of the present invention, such as InGaN It can be replaced by In _{x Aly} Ga _1-xy N, and GaN can be replaced by In _y Al _z Ga _1-yz N or Al _x Ga _1-x N. The purpose is to form a relaxed stress modulation layer and enhance the In segregation effect of the epitaxial InGaN light-emitting layer thereon.

The GaN-based single-chip white light emitting diode epitaxial structure material of the above-mentioned embodiment, that is, the initial growth layer, intrinsic GaN buffer layer, n-type GaN layer, InGaN/ GaN relaxed superlattice stress modulation layer, InGaN multi-quantum structure light emitting layer, p-type AlGaN interlayer and p-type GaN layer. This method retains the preparation process of the existing conventional blue light-emitting diode structural materials, and only improves the structural design of the GaN-based light-emitting material, by adding a relaxed InGaN/GaN supercrystal between the N-type GaN layer and the quantum well light-emitting layer The lattice stress modulation layer enhances the segregation effect of In and forms InGaN quantum dots of different compositions. These quantum dots emit a mixture of different wavelengths of light to achieve white light emission. The present invention uses the InGaN/GaN superlattice stress modulation layer to replace the existing single-layer InGaN stress modulation layer, which not only has the function of stress modulation, but also can filter dislocations, and can enhance the performance of single-chip white light devices. performance. The present invention fundamentally reduces the cost of white light emitting diodes without increasing the complexity of epitaxial structure material preparation and device process preparation, increases light emission efficiency and utilization efficiency, and overcomes the shortcomings of conventional phosphor powder conversion to obtain white light emitting diodes , improving the overall performance of white light emitting diodes.

Claims (4)

1, a kind of GaN based Single chip white light emitting diode epitaxial material, the initial growth layer, intrinsic GaN resilient coating, n type GaN layer, stress relaxation layer, InGaN volume minor structure luminescent layer, p type AlGaN interlayer and the p type GaN layer that comprise a substrate and on described substrate, grow successively; It is characterized in that: described stress relaxation layer is an InGaN/GaN superlattice stress modulation layer, and this superlattice stress modulation layer is made up of the InGaN layer and the GaN layer of alternating growth, and wherein the growth cycle of the InGaN layer of alternating growth and GaN layer is 6-500; In component in the described InGaN layer is in 1%～35% scope; The thickness of described InGaN/GaN superlattice stress modulation layer is 10nm-3 μ m.

2, a kind of GaN based Single chip white light emitting diode epitaxial material, the initial growth layer, intrinsic GaN resilient coating, n type GaN layer, stress relaxation layer, InGaN volume minor structure luminescent layer, p type AlGaN interlayer and the p type GaN layer that comprise a substrate and on described substrate, grow successively; It is characterized in that: described stress relaxation layer is a superlattice stress modulation layer, and this superlattice stress modulation layer is by alternating growth In _xGa _1-xN layer and In _yGa _1-yThe N layer is formed, and wherein the thickness of superlattice stress modulation layer is 10nm-3 μ m, described In _xGa _1-xN/In _yGa _1-yThe cycle of N alternating growth layer is 6-500; In component x and the y of described InGaN satisfy x＞y, and x regulates and control in 1%～35% scope, and y regulates and control in 0～35% scope, and the stress of superlattice is relaxation.

3, by claim 1 or 2 described GaN based Single chip white light emitting diode epitaxial materials, it is characterized in that: the InGaN in the described InGaN/GaN superlattice relaxed layer is In _xAl _yGa _1-x-yN;

GaN in the described InGaN/GaN superlattice relaxed layer is In _yAl _zGa _1-y-zN or Al _xGa _1-xN.

4, by claim 1 or 2 described GaN based Single chip white light emitting diode epitaxial materials, it is characterized in that: described substrate is sapphire substrate, SiC substrate or silicon chip;

Described initial growth layer is AlN layer or GaN layer; Its thickness 20nm-2 μ m;

Described intrinsic GaN layer is the transition zone of extension on foreign substrate that GaN layer, AlN layer, AlGaN layer, InGaN layer, InAlN layer, InAlGaN layer or this several alloy combination form; Its thickness 50nm-2 μ m;

Described n type GaN layer is the contact layer of the n type ohmic contact of GaN layer, AlN layer, AlGaN layer, InGaN layer, InAlN layer, InAlGaN layer or these several alloy combination; Its thickness 50nm-3 μ m;

Described InGaN volume minor structure luminescent layer is by barrier layer In _yGa _1-yN and quantum well layer In _xGa _1-xThe active layer of the light-emitting diode that N forms, y＜x wherein, 0.1＜x＜0.3,0＜y＜0.15; Described quantum well layer In _xGa _1-xN form with soakage layer by quantum dot or by fractional condensation mutually and the quantum structure of two different components that produce form; Described barrier layer In _yGa _1-yN and quantum well layer In _xGa _1-xThe doping content of N layer is 0～1 * 10 ¹⁸/ cm ³, the thickness 5-15nm of barrier layer, quantum well layer thickness 2-5nm; The periodicity of quantum well is 1～20;

Described p type AlGaN interlayer is Al _mGa _1-mThe N interlayer, wherein m is 0～0.2; Its thickness 5nm-1 μ m;

Described p type GaN layer is the contact layer of the p type ohmic contact of GaN layer, InAlN layer, AlGaN layer, InAlGaN layer or these several alloy combination.Its thickness 10nm-1 μ m.

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