CN103972335A - Light-emitting diode (LED) epitaxial layer structure and LED chip with same - Google Patents

Abstract

The present invention provides an LED epitaxial layer structure and an LED chip having the structure, the epitaxial layer structure includes a sequentially grown MQW layer, an electron blocking layer and a P-type GaN hole injection layer, and the P-type GaN hole injection layer includes The hole injection layer, the P-type GaN hole injection layer also includes a P-type AlGaN/GaN superlattice layer grown between the electron blocking layer and the hole injection layer. In the LED epitaxial layer structure provided by the present invention, an MQW protective layer is arranged between the electron blocking layer and the MQW layer, and a P-type AlGaN/GaN superlattice layer is arranged on the electron blocking layer, so that the P-type AlGaN/GaN superlattice layer The formed two-dimensional carrier gas is conducive to the uniform expansion of holes and improves the combination efficiency of electrons and holes.

Description

LED epitaxial layer structure and LED chip with the structure

technical field

The invention relates to the field of LED (Light Emitting Diode), in particular to an LED epitaxial layer structure and an LED chip with the structure.

Background technique

The GaN semiconductor material with wide bandgap has good chemical stability, thermal stability and high breakdown voltage. It is the third-generation new semiconductor material after the first-generation silicon material and the second-generation gallium arsenide material. The bandgap of its ternary alloy Indium Gallium Nitride (InXGa1-XN) is continuously adjustable from 0.7eV to 3.4eV, and the emission wavelength covers the visible and near-ultraviolet regions. It is considered to be an ideal material for manufacturing high-brightness blue and green light-emitting diodes and white light-emitting diodes, and has been widely used in lighting, display screens, backlight sources, signal lights and other fields.

As shown in Figure 1, the conventional GaN-based LED epitaxial layer structure is set on a sapphire substrate 1', including a low-temperature GaN buffer layer 2', a u-GaN layer 3', a second u-GaN layer 4', N-type GaN layer 5', electron storage layer 6', MQW (multiple quantum well) layer 7', electron blocking layer 8', P-type hole injection layer 9' and P-type contact layer 10 '. Under the working condition of high current density, this epitaxial layer structure cannot effectively block some electrons from entering the P-type hole injection layer 9' to form non-radiative recombination, thereby reducing the luminous efficiency of the LED device. At the same time, the P-type hole injection layer 9' needs to be grown at 900-1050° C., which is a relatively high growth temperature, which will cause internal damage to the grown MQW layer 7'. Therefore, the luminous efficiency of the LED device is reduced.

Contents of the invention

The purpose of the present invention is to provide an LED epitaxial layer structure and an LED chip with the structure, so as to solve the problem that the P-type GaN layer in the prior art cannot effectively block some electrons from entering the hole injection layer to form a non-radiative recombination and high-temperature P-type GaN layer. A technical issue of growth conditions causing damage to the MQW layer.

In order to achieve the above object, according to one aspect of the present invention, a LED epitaxial layer structure is provided, including an MQW layer, an electron blocking layer and a P-type GaN hole injection layer grown in sequence, and the P-type GaN hole injection layer includes holes The hole injection layer, the P-type GaN hole injection layer also includes a P-type AlGaN/GaN superlattice layer grown between the electron blocking layer and the hole injection layer.

Further, the P-type AlGaN/GaN superlattice layer includes a plurality of sequentially stacked structural units, and each structural unit includes a sequentially stacked superlattice P-type AlGaN layer and a superlattice P-type GaN layer.

Further, the thickness ratio of the superlattice P-type AlGaN layer to the superlattice P-type GaN layer in the P-type AlGaN/GaN is 1:1:2˜2:1.

Further, the thickness of the P-type AlGaN/GaN superlattice layer is 20-100 nm.

Further, the doping concentration of Mg in the superlattice P-type GaN layer is 1.0E18-1E20atom/cm ³ , and the doping concentration of Al component in the superlattice P-type AlGaN layer is 1E19-1E20atom/cm ³ .

Further, an MQW protection layer is also included, the MQW protection layer is grown between the MQW layer and the electron blocking layer, and the MQW protection layer is an AlInGaN material layer.

Further, the thickness of the MQW protection layer is 10-50 nm.

Further, the doping concentration of the In component in the MQW protection layer is 1E19˜1E20 atom/cm ³ , and the doping concentration of the Al component is 1E19˜1E20 atom/cm ³ .

According to another aspect of the present invention, there is also provided a method for growing an LED epitaxial layer structure as claimed in any one of claims 1 to 8, comprising a sequentially grown MQW layer, an electron blocking layer, and a P-type GaN hole injection layer. Step, the growth step of the P-type GaN hole injection layer includes sequentially growing the P-type AlGaN/GaN superlattice layer and the hole injection layer, and the growth step of the P-type AlGaN/GaN superlattice layer: growing on the electron blocking layer P-type AlGaN/GaN superlattice layer; the step of growing the P-type AlGaN/GaN superlattice layer includes: sequentially growing multiple structural units, and the step of growing each structural unit includes sequentially growing superlattice P-type AlGaN layer and superlattice P-type GaN layer; in the step of growing the superlattice P-type AlGaN layer, the growth temperature is 780-900°C, the growth pressure is 300-900mbar, and the aluminum source, gallium source and NH ₃ are introduced; the superlattice is grown In the step of the P-type GaN layer, the growth temperature is 780-900° C., the growth pressure is 500-900 mbar, and the gallium source and NH ₃ are fed.

Further, it also includes the step of growing the MQW protective layer between the MQW layer and the electron blocking layer. In the step of growing the MQW protective layer: the growth temperature is 750-850° C., the growth pressure is 300-600 mbar, and the aluminum source, Indium source, gallium source and NH ₃ .

According to another aspect of the present invention, there is also provided an LED chip, comprising an epitaxial layer, and the structure of the epitaxial layer is the epitaxial layer according to any one of claims 1-10.

The present invention has the following beneficial effects:

In the LED epitaxial layer structure provided by the present invention, an MQW protective layer is arranged between the electron blocking layer and the MQW layer, and a P-type AlGaN/GaN superlattice layer is arranged on the electron blocking layer, so that the P-type AlGaN/GaN superlattice layer The formed two-dimensional carrier gas is conducive to the uniform expansion of holes and improves the combination efficiency of electrons and holes. At the same time, the P-type AlGaN/GaN superlattice layer can also effectively limit the non-radiative recombination of electrons and holes that pass through the electron blocking layer without occurring outside the MQW layer, and effectively improve the mobility of holes, increasing the number of holes and holes. The recombination efficiency of electrons improves the luminous efficiency of the device.

Using the blue light chip of the LED standard chip with the epitaxial layer structure provided by the present invention, under the driving current of 350mA, the COW brightness of the 28mil*28mil chip is increased from 205mW to 220mW, which is increased by 7.3%.

In addition to the objects, features and advantages described above, the present invention has other objects, features and advantages. Hereinafter, the present invention will be described in further detail with reference to the drawings.

Description of drawings

The accompanying drawings constituting a part of this application are used to provide further understanding of the present invention, and the schematic embodiments and descriptions of the present invention are used to explain the present invention, and do not constitute an improper limitation of the present invention. In the attached picture:

FIG. 1 is a schematic structural view of an LED epitaxial layer in the prior art;

Fig. 2 is a schematic structural view of an LED epitaxial layer in a preferred embodiment of the present invention; and

Fig. 3 is a schematic structural diagram of an LED epitaxial layer in a preferred embodiment of the present invention.

illustration:

1. Substrate; 2. Low-temperature GaN buffer layer; 3. First u-GaN layer; 4. Second u-GaN layer; 5. N-type GaN layer; 6. Electronic storage layer; 7. MQW layer; 8. MQW protection layer; 9. Electron blocking layer; 10. P-type AlGaN/GaN superlattice layer; 101. Superlattice P-type AlGaN layer; 102. Superlattice P-type GaN layer; 11. P-type GaN hole injection layer; 110, hole injection layer; 12, P-type contact layer.

Detailed ways

The embodiments of the present invention will be described in detail below with reference to the accompanying drawings, but the present invention can be implemented in many different ways defined and covered by the claims.

The present invention provides an LED epitaxial layer structure, including an MQW (Multiple Quantum Well) layer 7 , an electron blocking layer 9 and a P-type GaN hole injection layer 11 grown in sequence. The P-type GaN hole injection layer 11 includes a P-type AlGaN/GaN superlattice layer 10 and a hole injection layer 110 stacked on each other in sequence. The P-type AlGaN/GaN superlattice layer 10 is grown between the electron blocking layer 9 and the hole injection layer 110 .

The P-type AlGaN/GaN superlattice layer 10 refers to an AlGaN layer having a superlattice structure and a GaN layer stacked in sequence. The successively stacked superlattice P-type AlGaN layer 101 and superlattice P-type GaN layer 102 may be one set or multiple sets. Preferably, the P-type AlGaN/GaN superlattice layer 10 includes a plurality of sequentially stacked structural units, and each structural unit includes a sequentially stacked superlattice P-type AlGaN layer 101 and a superlattice P-type GaN layer 102 . The hole injection layer 110 refers to a high-temperature P-type GaN layer, which mainly serves to provide holes. Because its growth temperature is mostly 900-1050°C, it is called a high-temperature P-type GaN layer.

In the P-type AlGaN/GaN superlattice layer 10 disposed between the electron blocking layer 9 and the hole injection layer 110, since the superlattice P-type AlGaN layer 101 is doped with Al elements, the superlattice P-type AlGaN layer 101 is relatively The energy band of the superlattice P-type GaN layer 102 is widened, and the energy band of the P-type AlGaN/GaN superlattice layer 10 is similar to that of a city wall crenellation. In this way, the electrons passing through the electron blocking layer 9 play a secondary blocking effect, preventing the electrons from jumping to the P-type GaN hole injection layer 11 to undergo non-radiative recombination with holes and reducing the concentration of recombinable holes.

The P-type AlGaN/GaN superlattice layer 10 is arranged below the hole injection layer 110, and the two-dimensional carrier gas formed by the obtained P-type AlGaN/GaN superlattice layer 10 can be beneficial to the holes in the hole injection layer 110. Holes expand evenly. The P-type AlGaN/GaN superlattice layer 10 and the hole injection layer 110 work together to effectively increase the mobility of holes, thereby improving the recombination efficiency of electrons and holes in the LED epitaxial layer. Therefore, the luminous efficiency of the obtained LED light-emitting device is improved.

Referring to Fig. 2, the LED epitaxial layer structure provided by the present invention includes a substrate 1, a low-temperature GaN buffer layer 2, a first u-GaN layer 3, a second u-GaN layer 4, an N-type GaN layer 5, an electronic Storage layer 6 , MQW layer 7 , electron blocking layer 9 , MQW protection layer 8 , P-type AlGaN/GaN superlattice layer 10 , P-type GaN hole injection layer 11 and P-type contact layer 12 .

The P-type AlGaN/GaN superlattice layer 10 includes a plurality of structural units, and each structural unit includes a superlattice P-type AlGaN layer 101 and a superlattice P-type GaN layer 102 stacked in sequence. A superlattice P-type AlGaN layer 101 is grown on the top surface of the electron blocking layer 9 . A superlattice P-type GaN layer 102 is grown on the top surface of the superlattice P-type AlGaN layer 101 . Then grow the superlattice P-type AlGaN layer 101 in the second structural unit on the top surface of the superlattice P-type GaN layer 102 . The P-type AlGaN/GaN superlattice layer 10 with multiple structural units is obtained through multiple cycles. A hole injection layer 110 is grown on the top surface of the P-type AlGaN/GaN superlattice layer 10 . The P-type AlGaN/GaN superlattice layer 10 and the hole injection layer 110 are stacked to form the P-type GaN hole injection layer 11 . A P-type contact layer 12 is grown on the top surface of the P-type GaN hole injection layer 11 .

The thickness of the superlattice P-type AlGaN layer 101 and the superlattice P-type GaN layer 102 can be the layer thickness ratio in the conventional LED epitaxial layer structure. Preferably, the thickness ratio of the superlattice P-type AlGaN layer 101 and the superlattice P-type GaN layer 102 is 1:2˜2:1. At this time, the obtained P-type AlGaN/GaN superlattice layer 10 has a better effect on hole diffusion. More preferably, the thickness ratio is 1:0.8-1.2, and the most preferable thickness ratio is 1:1. At this time, the obtained P-type AlGaN/GaN superlattice layer 10 has the best effect on hole diffusion.

Preferably, the thickness of the superlattice P-type AlGaN layer 101 is 2-8 nm, the thickness of the superlattice P-type GaN layer 102 is 2-8 nm, and the number of periods of the structural unit is 5-10. The P-type AlGaN/GaN superlattice The thickness of layer 10 is 20-100 nm. At this time, there are 10 pairs of P-type AlGaN/GaN superlattice layers. Preferably, the thickness of the P-type AlGaN/GaN superlattice layer 10 is 20-50 nm. At this time, the expansion effect of the P-type AlGaN/GaN superlattice layer 10 on holes and the blocking effect on electrons are synergistically optimized. In order to prevent the P-type AlGaN/GaN superlattice layer 10 from being too thick and blocking light from exiting. It also avoids the problem that the P-type AlGaN/GaN superlattice layer 10 cannot generate sufficient two-dimensional carrier gas to enhance the expansion of holes because the P-type AlGaN/GaN superlattice layer 10 is too thin.

Preferably, the Mg doping concentration in the superlattice P-type GaN layer 102 is 1.0E18˜1E20 atom/cm3. The doping concentration of the Al component in the superlattice P-type AlGaN layer 101 is 1E19-1E20 atom/cm3. Doping at this concentration can not only ensure the generation of the superlattice structure, but also prevent the reduction of hole mobility in the superlattice P-type GaN layer 102 due to doping too much Mg element and affect the luminous efficiency. Although Al doping in the superlattice P-type AlGaN layer 101 can broaden the energy band and block electron migration, if the Al doping concentration is too high, it will increase the resistance of the LED chip and affect the performance of the LED chip. The superlattice P-type GaN layer 102 can be doped with Mg to form P-type GaN.

Preferably, the LED epitaxial layer structure provided by the present invention further includes an MQW protective layer 8 grown between the MQW layer 7 and the electron blocking layer 9 . The MQW protection layer 8 is an AlInGaN material layer.

The LED epitaxial layer structure with the MQW protective layer 8 is shown in Figure 3. It can be seen from Figure 3 that the LED epitaxial layer structure includes a substrate 1, a low-temperature GaN buffer layer 2, a first u-GaN layer 3, and a second u-GaN layer stacked in sequence. -GaN layer 4, N-type GaN layer 5, electron storage layer 6, MQW layer 7, MQW protection layer 8, electron blocking layer 9, P-type AlGaN/GaN superlattice layer 10, P-type GaN hole injection layer 11 and P-type contact layer 12 . The structure of the P-type AlGaN/GaN superlattice layer 10 is the same as the above structure. An MQW protection layer 8 is grown on the MQW layer 7 . An electron blocking layer 9 is grown on the top surface of the MQW protection layer 8 .

The MQW protective layer 8 made of AlInGaN is doped with Al and In, so it can adjust the energy band width of GaN in a large range, and thus has a better effect of blocking electrons. Usually, only Al or In is doped as the MQW protective layer 8 , and doping only one element has a limited effect on the energy band broadening of the MQW protective layer 8 . Simultaneous doping of two elements can make the energy band of the MQW protective layer 8 wider. Electron transitions in the MQW layer 7 are better prevented from leaving the MQW layer 7 . Reduce the occurrence of non-radiative recombination of electrons. The thickness of the MQW protection layer 8 can be a commonly used layer thickness.

The thickness of the MQW protective layer 8 is preferably 10 to 50 nm. At this time, the MQW protective layer 8 can not only play the role of blocking electrons, but also avoid blocking the emission of light due to the MQW protective layer 8 . More preferably, the thickness of the MQW protection layer 8 is 10-30 nm. At this time, the function of the MQW protective layer 8 to block electrons and lead to light emission is optimal.

Preferably, the doping concentration of the In component in the MQW protective layer 8 is 1E19˜1E20 atom/cm3. According to this doping concentration, it can prevent excessive In doping concentration from causing too many defects in the resulting MQW protective layer 8 to affect the performance of the LED chip, and at the same time ensure that the electronic blocking effect is exerted. The doping concentration of the Al component is 1E19-1E20 atom/cm3, which prevents excessively increasing the resistance of the LED chip while ensuring the electron blocking effect.

Another aspect of the present invention also provides a method for growing an LED epitaxial layer structure, including the steps of sequentially growing an MQW layer 7, an electron blocking layer 9, and a P-type GaN hole injection layer 11, and the P-type GaN hole injection layer The step of growing the layer 11 includes sequentially growing the P-type AlGaN/GaN superlattice layer 10 and the hole injection layer 110,

The growth step of the P-type AlGaN/GaN superlattice layer 10: growing the P-type AlGaN/GaN superlattice layer 10 on the electron blocking layer 9;

The step of growing the P-type AlGaN/GaN superlattice layer 10 includes: sequentially growing a plurality of structural units, and the step of growing each structural unit includes sequentially;

In step 101 of growing the superlattice P-type AlGaN layer, the growth temperature is 780-900° C., the growth pressure is 300-900 mbar, and aluminum source, gallium source and NH3 are introduced;

In the step 102 of growing the superlattice P-type GaN layer, the growth temperature is 780-900° C., the growth pressure is 300-900 mbar, and gallium source and NH3 are fed. More preferably, the growth pressure is 500-900 mbar. The superlattice structure obtained by growing under this pressure has a better effect of enhancing the brightness of the LED chip.

The growth temperature of the P-type AlGaN/GaN superlattice layer 10 is lower than the 900-1050° C. growth temperature of the hole injection layer 110 . The growth temperature of the hole injection layer 110 can prevent the thermal precipitation of In doped in the MQW layer 7 during the growth process due to excessive temperature, thereby reducing the performance of the MQW layer 7 . At the same time, the growth pressure makes the quality of the obtained P-type AlGaN/GaN superlattice layer 10 better, and prevents In and Al elements from being unable to be doped into due to excessive pressure.

The gallium source used was trimethylgallium (TMGa) or triethylgallium (TEGa). The indium source may be trimethylindium (TMIn). The aluminum source was trimethylaluminum (TMAl). The magnesium source is magnesium dicene (Cp2Mg).

Preferably, when the LED epitaxial wafer needs to grow the MQW protective layer 8, it also includes the step of growing the MQW protective layer 8 between the MQW layer 7 and the electron blocking layer 9. In the step of growing the MQW protective layer 8: the growth temperature is 750-850°C, growth pressure of 300-600mbar, feed aluminum source, indium source, gallium source and NH3.

The growth position of the MQW protective layer 8 is on the MQW layer 7 , so the temperature during the growth of the MQW protective layer 8 has a greater influence on the MQW layer 7 . Since the growth temperature of the MQW protective layer 8 is relatively low, only 750-850° C., it can prevent the adverse effect of the high temperature used for growing the hole injection layer 110 on the In in the MQW layer 7 . Therefore, the MQW layer 7 is protected from the growth process.

The LED epitaxial layer preparation method provided by the present invention comprises the following steps:

The following growth processes are carried out in MOCVD equipment by MOCVD method.

1. Place the sapphire substrate 1 in the MOCVD reaction chamber, and treat the sapphire substrate 1 with H ₂ , NH ₃ and other gases for 4 to 10 minutes at a temperature of 1000-1100° C.;

2. After the treatment is completed, the temperature of the reaction chamber is lowered to 500-650°C, the optimum temperature is 550°C, and TMGa and NH ₃ are introduced at a pressure of 300-900mbar, and the sapphire substrate 1 is grown with a thickness of 20-50nm. GaN buffer layer 2 (Nucleation);

3. After the GaN buffer layer 2 is grown, the temperature is raised to 950-1100° C., annealed for 60-300 s, and a GaN crystal nucleus is formed on the substrate 1;

4. After the annealing is completed, the temperature is adjusted to 950-1050° C., TMGa and NH ₃ are introduced, the pressure is 300-900 mbar, and the first u-GaN layer 3 with a thickness of 0.8-1.5 μm is grown on the GaN buffer layer 2 ;

5. Then raise the temperature to 1000-1100°C, and the pressure to 300mbar-900mbar, and grow the second u-GaN layer 4 with a thickness of 2-3um.

6. After the growth of the second u-GaN layer 4 is finished, adjust the temperature to 1000-1100°C, feed TMGa, NH ₃ , SiH ₄ , and grow SiN doped with a thickness of 2-3um on the second u-GaN layer 4 GaN is used as the N-type GaN layer 5, and the doping concentration is 5E18-2E19 atom/cm ³ ;

7. After the growth of n-GaN is completed, grow 2-6 InGaN/GaN electron storage layers 6, grow the In _x Ga _(1-x) N/GaN layer doped under the conditions of pressure 300mbar-400mbar and temperature 800-850°C, In _x Ga _(1~x) N thickness 0.5~10nm, GaN thickness 20~50nm;

8. After the growth of the electron storage layer is completed, the MQW layer 7 of the active light-emitting layer is grown periodically, the pressure is 300mbar-400mbar, the well layer of 2-3nmIn _x Ga _(1-x) N is grown at 750°C, and the well layer of 10-13nmGaN is grown at 800-850°C Barrier layer. In _x Ga _(1～x) N/GaN period number is 9～18;

9. After the growth of the active layer is completed, grow another MQW protective layer 8 made of AlInGaN; adjust the temperature to 750-850°C, feed TMGa, NH ₃ , TMAl, TMIn, pressure 300-600mbar, and grow a thickness of 10 ～50nm, In component concentration: 1E19～1E20atom/cm ³ , Al component concentration: 1E19～1E20atom/cm ³ ;

10. After the growth of the MQW protective layer 8 is completed, another layer of P-type AlInGaN is grown as the electron blocking layer 9; the temperature is adjusted to 780-950°C, and TMGa, NH ₃ , Cp2Mg, TMAl and TMIn are introduced, and the pressure is 100-500mbar to grow Thickness is about 20-40nm, Al component concentration: 1E19-2E20atom/cm ³ , Mg component concentration: 1E19-1E20atom/cm ³ ; In component concentration: 5E19-2E20atom/cm ³ ;

11. After the growth of P-type AlInGaN is completed, another layer of P-type AlGaN/GaN superlattice layer 10 is grown; the temperature is adjusted to 780-900°C, TMGa, NH3, Cp2Mg and TMAl are introduced, and the growth pressure is 300-900mbar, one The period includes the superlattice P-type AlGaN layer 101 and the superlattice P-type GaN layer 102 as a structural unit. The thickness ratio of the superlattice P-type AlGaN layer 101 and the superlattice P-type GaN layer 102 is 1:1, and the single-layer thickness of the superlattice P-type AlGaN layer 101 and the superlattice P-type GaN layer 102 is 2 nm to 8 nm. , the period is 5-10, the total thickness of the P-type AlGaN/GaN superlattice layer 10 is about 20-100 nm, the Mg doping concentration is 1.0E18-1E20 atom/cm ³ , the Al component concentration: 1E19-1E20 atom/cm ³ ;

12. After the AlGaN/GaN superlattice layer 10 is grown, grow another layer of P-type GaN hole injection layer 11, adjust the temperature to 900-1050°C, inject TMGa, NH ₃ , and Cp2Mg, and grow at a pressure of 500-900 mbar. Grow a P-type GaN layer of 30-100nm, with a Mg doping concentration of 1E19-2E20 atom/cm ³ ;

13. After the growth of the P-type GaN hole injection layer 11 is completed, a P-type contact layer 12 is grown again; the temperature is adjusted to 650-680° C., TMGa, NH ₃ , Cp2Mg and TMIn are introduced, and the growth pressure is 300-500 mbar. 5-10nm magnesium-doped InGaN layer;

14. After the growth of the contact layer is completed, lower the temperature to 700-750° C., and in a nitrogen atmosphere for 20-30 minutes, activate P-type GaN to obtain an LED epitaxial wafer with an LED epitaxial layer structure.

Another aspect of the present invention also provides an LED chip with an LED epitaxial layer structure. The LED chip can be prepared by conventional methods. It only needs to have the aforementioned LED epitaxial layer structure.

The luminous efficiency of the LED chip adopting the LED epitaxial layer structure can be increased by 7.3%.

Example

All materials used in the following examples are commercially available. The epitaxial wafers obtained in the following examples and comparative examples were assembled according to standard methods to obtain LED chips. The growth of the epitaxial layer was carried out on AixtronCriusII type MOCVD (metal organic chemical vapor deposition) equipment.

Example 1

1. Place the sapphire substrate 1 in the MOCVD reaction chamber, and treat the sapphire substrate 1 with H ₂ , NH ₃ and other gases for 4 minutes at a temperature of 1000°C;

2. After the treatment is completed, the temperature of the reaction chamber is lowered to 500°C, and TMGa and NH ₃ are introduced into the chamber at a pressure of 300mbar, and a GaN buffer layer 2 (Nucleation) with a thickness of 20nm is grown on the sapphire substrate 1;

3. After growing the GaN buffer layer 2, raise the temperature to 950°C and anneal for 60s to form a GaN crystal nucleus on the substrate 1;

4. After the annealing is completed, the temperature is adjusted to 950° C., and TMGa and NH ₃ are introduced, and the pressure is 300 mbar, and the first u-GaN layer 3 with a thickness of 0.8 μm is grown on the GaN buffer layer 2 ;

5. Then raise the temperature to 1000° C. and the pressure to 300 mbar, and grow the second u-GaN layer 4 with a thickness of 2 μm.

6. After the growth of the second u-GaN layer 4N is completed, adjust the temperature to 1000°C, feed TMGa, NH ₃ , SiH ₄ , and grow SiN-doped GaN with a thickness of 2um on the second u-GaN layer 4 as N Type GaN layer 5, doping concentration 5E18atom/cm ³ ;

7. After the growth of n-GaN is completed, grow 2-6 InGaN/GaN electron storage layers 6, grow In _x Ga _(1-x) N/GaN layer doped with In _x Ga _{(1 ~x)} N thickness 0.5nm, GaN thickness 20nm;

8. After the growth of the electron storage layer is completed, periodically grow the MQW layer 7 of the active light-emitting layer, the pressure is 300mbar, the well layer of 2nmIn _x Ga _(1～x) N is grown at 750°C, and the barrier layer of 11nmGaN is grown at 800°C. In _x Ga _{(1 ~x)} The number of N/GaN cycles is 9;

9. After the growth of the active layer is completed, grow another layer of MQW protection layer 8 made of AlInGaN; adjust the temperature to 750°C, feed TMGa, NH ₃ , TMAl, TMIn, pressure 300mbar, growth thickness 10nm, In composition Concentration: 5.0E19atom/cm ³ , Al component concentration: 8.0E19atom/cm ³ ;

10. After the growth of the MQW protective layer 8 is completed, another layer of P-type AlGaN is grown as the electron blocking layer 9; the temperature is adjusted to 780°C, TMGa, NH ₃ , Cp2Mg and TMAl are introduced, the pressure is 100mbar, the growth thickness is about 20nm, and the Al group Partial concentration: 1.5E20atom/cm ³ , Mg component concentration: 1.0E20atom/cm ³ ;

11. After the growth of P-type AlGaN is completed, another layer of P-type AlGaN/GaN superlattice layer 10 is grown; the temperature is adjusted to 780°C, TMGa, NH ₃ , Cp2Mg and TMAl are introduced, and the growth pressure is 500mbar, and one cycle includes one As structural units, the superlattice P-type AlGaN layer 101 and the superlattice P-type GaN layer 102 serve as a structural unit. The thickness ratio of the superlattice P-type AlGaN layer 101 and the superlattice P-type GaN layer 102 is 1:0.8, and the single-layer thickness of the superlattice P-type AlGaN layer 101 is 2nm and the single-layer thickness of the superlattice P-type GaN layer 102. The layer thickness is 1.6nm, the period is 5, the total thickness of the P-type AlGaN/GaN superlattice layer 10 is about 20nm, the Al component concentration: 1.0E19atom/cm ³ , and the Mg doping concentration in the superlattice P-type GaN layer 102 1.0E20atom/cm ³ ;

12. After the AlGaN/GaN superlattice layer 10 is grown, grow a P-type GaN hole injection layer 11, adjust the temperature to 900°C, inject TMGa, NH ₃ , Cp2Mg, and grow 30nm P Type GaN layer, Mg doping concentration 1E19atom/cm ³ ;

13. After the growth of the P-type GaN hole injection layer 11 is completed, a P-type contact layer 12 is grown; the temperature is adjusted to 650°C, TMGa, NH ₃ , Cp2Mg and TMIn are introduced, the growth pressure is 300mbar, and a 5nm magnesium doped layer is grown. InGaN layer;

14. After the growth of the contact layer is completed, lower the temperature to 700° C., and activate the P-type GaN for 20 minutes in a nitrogen atmosphere to obtain an LED epitaxial wafer 1 with an LED epitaxial layer structure.

Example 2

1. Place the sapphire substrate 1 in the MOCVD reaction chamber, and treat the sapphire substrate 1 with H ₂ , NH ₃ and other gases for 10 minutes at a temperature of 1100°C;

2. After the treatment is completed, the temperature of the reaction chamber is lowered to 650°C, and TMGa and NH ₃ are introduced into the chamber at a pressure of 900mbar to grow a GaN buffer layer 2 (Nucleation) with a thickness of 50nm on the sapphire substrate 1;

3. After growing the GaN buffer layer 2, raise the temperature to 1100°C and anneal for 300s to form a GaN crystal nucleus on the substrate 1;

4. After the annealing is completed, the temperature is adjusted to 1050° C., TMGa and NH ₃ are introduced, the pressure is 900 mbar, and the first u-GaN layer 3 with a thickness of 1.5 μm is grown on the GaN buffer layer 2 ;

5. The temperature is raised to 1100° C., the pressure is 900 mbar, and the second u-GaN layer 4 with a thickness of 3 μm is grown.

6. After the growth of the second u-GaN layer 4 is completed, adjust the temperature to 1100°C, feed TMGa, NH ₃ , SiH ₄ , and grow SiN-doped GaN with a thickness of 3um on the second u-GaN layer 4 as N Type GaN layer 5, doping concentration 2E19atom/cm ³ ;

7. After the growth of n-GaN is completed, grow 6 InGaN/GaN electron storage layers 6, grow In _x Ga _{(1-x) N/GaN layers doped with In x Ga (1-x)} under the conditions of pressure 400mbar and temperature 850°C, and In _x Ga _{(1-x )} N thickness 10nm, GaN thickness 50nm;

8. After the growth of the electron storage layer is completed, periodically grow the MQW layer 7 of the active light-emitting layer, the pressure is 300mbar~400mbar, the well layer of 3nmIn _x Ga _(1~x) N is grown at 750°C, and the barrier layer of 13nmGaN is grown at 850°C. In _x Ga _(1～x) The number of N/GaN periods is 18;

9. After the active layer is grown, grow another MQW protective layer 8 made of AlInGaN; the temperature is adjusted to 850°C, TMGa, NH ₃ and TMAl, TMIn are introduced, the pressure is 600mbar, the growth thickness is 30nm, and the In composition Concentration: 6.0E19atom/cm ³ , Al component concentration: 1E20atom/cm ³ ;

10. After the growth of the MQW protective layer 8 is completed, another layer of P-type AlGaN is grown as the electron blocking layer 9; the temperature is adjusted to 950°C, TMGa, NH ₃ , Cp2Mg and TMAl are introduced, the pressure is 500mbar, the growth thickness is about 40nm, and the Al group Partial concentration: 3E20atom/cm ³ , Mg component concentration: 1E20atom/cm ³ ;

11. After the growth of P-type AlGaN is completed, another layer of P-type AlGaN/GaN superlattice layer 10 is grown; the temperature is adjusted to 900°C, TMGa, NH3, Cp2Mg and TMAl are introduced, the growth pressure is 900mbar, and one cycle includes one structure unit, the superlattice P-type AlGaN layer 101 and the superlattice P-type GaN layer 102 serve as a structural unit. The thickness ratio of the superlattice P-type AlGaN layer 101 and the superlattice P-type GaN layer 102 is 1:1.2, and the single-layer thickness of the superlattice P-type AlGaN layer 101 is 2nm and that of the superlattice P-type GaN layer 102. The layer thickness is 2.4nm, the period is 10, the total thickness of the P-type AlGaN/GaN superlattice layer 10 is about 45nm, the Mg doping concentration is 1E20atom/cm ³ , and the Al component concentration is 1E20atom/cm ³ ;

12. After the AlGaN/GaN superlattice layer 10 is grown, grow a P-type GaN hole injection layer 11, adjust the temperature to 1050°C, inject TMGa, NH ₃ , and Cp2Mg, and grow 100nm of P Type GaN layer, Mg doping concentration 2E20atom/cm ³ ;

13. After the growth of the P-type GaN hole injection layer 11 is completed, a P-type contact layer 12 is grown; the temperature is adjusted to 680°C, TMGa, NH ₃ , Cp2Mg and TMIn are introduced, the growth pressure is 500mbar, and a 10nm magnesium doped layer is grown. InGaN layer;

14. After the growth of the contact layer is completed, lower the temperature to 750° C. and activate the P-type GaN for 30 minutes in a nitrogen atmosphere to obtain an LED epitaxial wafer 2 with an LED epitaxial layer structure.

Example 3

1. Place the sapphire substrate 1 in the MOCVD reaction chamber, and treat the sapphire substrate 1 with H ₂ , NH ₃ and other gases for 6 minutes at a temperature of 1050°C;

2. After the treatment is completed, the temperature of the reaction chamber is lowered to the optimum temperature of 550° C., and TMGa and NH ₃ are fed in at a pressure of 800 mbar to grow a GaN buffer layer 2 (Nucleation) with a thickness of 30 nm on the sapphire substrate 1;

3. After the GaN buffer layer 2 is grown, the temperature is raised to 1000°C and annealed for 200s to form a GaN crystal nucleus on the substrate 1;

4. After the annealing is completed, the temperature is adjusted to 1000°C, TMGa and NH ₃ are introduced, and the pressure is 700mbar, and the first u-GaN layer 3 with a thickness of 1.0um is grown on the GaN buffer layer 2;

5. Then raise the temperature to 1050° C. and the pressure to 600 mbar, and grow the second u-GaN layer 4 with a thickness of 2.5 μm.

6. After the growth of the second u-GaN layer 4N is completed, adjust the temperature to 1050°C, feed TMGa, NH ₃ , SiH ₄ , and grow SiN-doped GaN with a thickness of 2.5um on the second u-GaN layer 4 as N-type GaN layer 5, doping concentration 7E18atom/cm ³ ;

7. After the growth of n-GaN is completed, grow 4 InGaN/GaN electron storage layers 6, grow In _x Ga _{(1-x) N/GaN layer doped with In x Ga (1-x)} under the conditions of pressure 500mbar and temperature 840°C, In _x Ga _{(1-x )} N thickness 0.7nm, GaN thickness 30nm;

8. After the growth of the electron storage layer is completed, periodically grow the MQW layer 7 of the active light-emitting layer, grow a well layer of 2.5nmIn _x Ga _(1~x) N at a pressure of 350mbar at 750°C, and grow a 12nmGaN barrier layer at 850°C. In _x Ga _(1~ x) _x) The number of N/GaN cycles is 10;

9. After the growth of the active layer is completed, grow another MQW protective layer 8 made of AlInGaN; adjust the temperature to 800°C, feed TMGa, NH ₃ , TMAl, TMIn, the pressure is 400mbar, the growth thickness is 20nm, and the In composition Concentration: 8E19atom/cm ³ , Al component concentration: 9E19atom/cm ³ ;

10. After the growth of the MQW protection layer 8 is completed, another layer of P-type AlGaN is grown as the electron blocking layer 9; the temperature is adjusted to 880°C, TMGa, NH ₃ , Cp2Mg and TMAl are introduced, the pressure is 400mbar, the growth thickness is about 30nm, and the Al group Partial concentration: 2E20atom/cm ³ , Mg component concentration: 7E19atom/cm ³ ;

11. After the growth of P-type AlGaN is completed, another layer of P-type AlGaN/GaN superlattice layer 10 is grown; the temperature is adjusted to 790°C, TMGa, NH ₃ , Cp2Mg and TMAl are introduced, the growth pressure is 300mbar, and one cycle includes one structure unit. The superlattice P-type AlGaN layer 101 and the superlattice P-type GaN layer 102 serve as a structural unit. The thickness ratio of the superlattice P-type AlGaN layer 101 and the superlattice P-type GaN layer 102 is 1:1, and the single-layer thickness of the superlattice P-type AlGaN layer 101 is 2nm and the single-layer thickness of the superlattice P-type GaN layer 102 The layer thickness is 2nm, the period is 5, the total thickness of the P-type AlGaN/GaN superlattice layer 10 is about 20nm, the Mg doping concentration in the superlattice P-type GaN layer 102 is 1.0E18atom/cm ³ , and the Al component concentration is: 7E19 atom/cm ³ ;

12. After the AlGaN/GaN superlattice layer 10 is grown, grow a P-type GaN hole injection layer 11, adjust the temperature to 1000°C, inject TMGa, NH ₃ , and Cp2Mg, and grow 60nm P Type GaN layer, Mg doping concentration 1E20atom/cm ³ ;

13. After the growth of the P-type GaN hole injection layer 11 is completed, another layer of P-type contact layer 12 is grown; the temperature is adjusted to 660°C, TMGa, NH ₃ , Cp2Mg and TMIn are introduced, and the growth pressure is 400mbar to grow 8nm magnesium-doped InGaN layer;

14. After the growth of the contact layer is completed, lower the temperature to 740° C., and activate the P-type GaN for 25 minutes in a nitrogen atmosphere to obtain an LED epitaxial wafer 3 with an LED epitaxial layer structure.

Example 4

The difference with embodiment 1 is:

The In component concentration in step 9: 1.0E19atom/cm ³ , the Al component concentration: 1.0E19atom/cm ³ .

In step 11: the thickness ratio of the superlattice P-type AlGaN layer 101 and the superlattice P-type GaN layer 102 is 1:2, the single layer thickness of the superlattice P-type AlGaN layer 101 is 5nm and the superlattice P-type GaN The single layer thickness of the layer 102 is 10 nm, the period is 5, and the total thickness of the P-type AlGaN/GaN superlattice layer 10 is about 75 nm. The MQW protective layer 8 has a thickness of 50 nm. An LED epitaxial wafer 4 was obtained.

Example 5

The difference with embodiment 1 is:

In step 9: In component concentration: 1E20 atom/cm ³ .

In step 11: the thickness ratio of the superlattice P-type AlGaN layer 101 and the superlattice P-type GaN layer 102 is 1:1, the single layer thickness of the superlattice P-type AlGaN layer 101 is 5nm and the superlattice P-type GaN The single layer thickness of the layer 102 is 5 nm, the period is 10, and the total thickness of the P-type AlGaN/GaN superlattice layer 10 is about 100 nm. An LED epitaxial wafer 5 was obtained.

Example 6

The difference from Example 1 is that the thickness ratio of the superlattice P-type AlGaN layer 101 to the superlattice P-type GaN layer 102 is 2:1, the single layer thickness of the superlattice P-type AlGaN layer 101 is 5nm and supercrystalline The single layer thickness of the lattice P-type GaN layer 102 is 2.5 nm, the period is 3, and the total thickness of the P-type AlGaN/GaN superlattice layer 10 is about 23 nm. The LED epitaxial wafer 6 was obtained.

Comparative example 1

The difference from Embodiment 1 is that no P-type AlGaN/GaN superlattice layer 10 and MQW protection layer 8 are provided. The LED epitaxial wafer 7 was obtained.

Comparative example 2

The difference from Embodiment 1 is that no P-type AlGaN/GaN superlattice layer 10 is provided. An LED epitaxial wafer 8 was obtained.

Comparative example 3

The difference from Example 1 is that the thickness ratio of the superlattice P-type AlGaN layer to the P-type GaN layer in the P-type AlGaN/GaN is 1:3. The LED epitaxial wafer 9 was obtained.

Comparative example 4

The difference from Example 1 is that the thickness ratio of the superlattice P-type AlGaN layer to the P-type GaN layer in the P-type AlGaN/GaN is 3:1. The LED epitaxial wafer 10 was obtained.

The obtained LED epitaxial wafers 1-10 are made into 28mil*28mil chips according to the formal LED chip manufacturing process, and blue LED chips 1-10 with a dominant wavelength of 450nm. Under the driving current of 350mA, the luminous efficiency of the COW brightness of each LED chip was measured by a COW data point measuring machine (model: Huite FWP6000). The average luminous efficiency of each LED chip obtained is listed in Table 1.

Table 1 Luminous efficiency of LED chips 1 to 10

LED chip number Luminous efficiency/(mW) 1 218 2 219 3 220 4 220 5 215 6 215 7 205 8 207 9 210 10 209

It can be seen from Table 1 that the luminous efficiency of the LED chip with the P-type AlGaN/GaN superlattice layer 10 is improved relative to the LED chip 6 without the P-type AlGaN/GaN superlattice layer 10, which shows that by setting the P-type AlGaN/GaN superlattice The luminous efficiency of the LED chip obtained in layer 10 is improved, the effective coincidence efficiency of holes and electrons in the LED chip is improved, and the non-radiative recombination rate of electrons is reduced.

The luminous efficiency of the LED chip 4 is higher than that of the LED chip 6, indicating that the luminous efficiency of the LED chip can be further enhanced by setting the MQW protective layer 8, and the migration of non-radiative recombination electrons can be blocked, thereby improving the luminous efficiency.

The luminous efficiencies of LED chips 8 and 9 are only 210 or 209mW, indicating that the thickness ratio of the superlattice P-type AlGaN layer and P-type GaN layer in the set P-type AlGaN/GaN is not in the range of 1:2~2:1. The effect of luminous efficiency is not obvious.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (11)

1. A LED epitaxial layer structure, comprising a sequentially grown MQW layer, an electron blocking layer and a P-type GaN hole injection layer, the P-type GaN hole injection layer comprising a hole injection layer, characterized in that the The P-type GaN hole injection layer further includes a P-type AlGaN/GaN superlattice layer grown between the electron blocking layer and the hole injection layer. 2. The LED epitaxial layer structure according to claim 1, wherein the P-type AlGaN/GaN superlattice layer comprises a plurality of sequentially stacked structural units, each of which comprises sequentially stacked A superlattice P-type AlGaN layer and a superlattice P-type GaN layer. 3. The LED epitaxial layer structure according to claim 1, wherein the thickness ratio of the superlattice P-type AlGaN layer and the superlattice P-type GaN layer in the P-type AlGaN/GaN is 1 :2～2:1. 4 . The LED epitaxial layer structure according to claim 3 , wherein the thickness of the P-type AlGaN/GaN superlattice layer is 20-100 nm. 5. The LED epitaxial layer structure according to claim 1, wherein the Mg doping concentration in the superlattice P-type GaN layer is 1.0E18-1E20atom/cm ³ , and the superlattice P-type AlGaN layer The doping concentration of the Al component is 1E19-1E20 atom/cm ³ . 6. The LED epitaxial layer structure according to any one of claims 1 to 5, further comprising an MQW protection layer, the MQW protection layer grown between the MQW layer and the electron blocking layer, The MQW protection layer is an AlInGaN material layer. 7 . The LED epitaxial layer structure according to claim 6 , wherein the MQW protection layer has a thickness of 10-50 nm. 8. The LED epitaxial layer structure according to claim 7, characterized in that the doping concentration of the In component in the MQW protection layer is 1E19-1E20 atom/cm ³ , and the doping concentration of the Al component is 1E19-1E20 atom /cm ³ . 9. A method for growing the LED epitaxial layer structure according to any one of claims 1 to 8, comprising the steps of sequentially growing the MQW layer, the electron blocking layer and the P-type GaN hole injection layer, characterized in that, The step of growing the P-type GaN hole injection layer includes sequentially growing the P-type AlGaN/GaN superlattice layer and the hole injection layer, The step of growing the P-type AlGaN/GaN superlattice layer: growing the P-type AlGaN/GaN superlattice layer on the electron blocking layer; The step of growing the P-type AlGaN/GaN superlattice layer includes: sequentially growing a plurality of structural units, and the step of growing each of the structural units includes sequentially growing a superlattice P-type AlGaN layer and a superlattice P Type GaN layer; In the step of growing the superlattice P-type AlGaN layer, the growth temperature is 780-900° C., the growth pressure is 300-900 mbar, and aluminum source, gallium source and NH ₃ are introduced; In the step of growing the superlattice P-type GaN layer, the growth temperature is 780-900° C., the growth pressure is 500-900 mbar, and the gallium source and NH ₃ are fed. 10. The method according to claim 9, further comprising the step of growing an MQW protection layer between the MQW layer and the electron blocking layer, in the step of growing the MQW protection layer: growth temperature The temperature is 750-850° C., the growth pressure is 300-600 mbar, and the aluminum source, indium source, gallium source and NH ₃ are fed. 11. An LED chip, comprising an epitaxial layer, wherein the epitaxial layer structure is the epitaxial layer according to any one of claims 1-10.