阅读说明：本技术 一种led外延生长方法 (LED epitaxial growth method ) 是由 徐平 胡耀武 谢鹏杰 于 2019-09-24 设计创作，主要内容包括：本申请公开了一种LED外延生长方法,依次包括：处理衬底、生长低温缓冲层GaN、生长不掺杂GaN层、生长掺杂Si的N型GaN层、生长多量子阱层、生长AlGaN电子阻挡层、生长掺杂Mg的P型GaN层,降温冷却,其中生长多量子阱层依次包括生长低温GaN垒层、生长压力渐变InGaN阱层、生长温度渐变InGaN阱层、生长温度和压力同时渐变InGaN阱层、生长高温GaN垒层、生长AlN层的步骤。本发明方法解决现有LED外延生长方法中存在的量子阱生长质量不高及量子阱辐射复合效率低下的问题,从而提高LED的发光效率,并减少外延片翘曲。(The application discloses an LED epitaxial growth method, which sequentially comprises the following steps: the method comprises the steps of treating a substrate, growing a low-temperature buffer layer GaN, growing an undoped GaN layer, growing an N-type GaN layer doped with Si, growing a multi-quantum well layer, growing an AlGaN electronic barrier layer, growing a P-type GaN layer doped with Mg, and cooling, wherein the growing multi-quantum well layer sequentially comprises the steps of growing a low-temperature GaN barrier layer, growing a InGaN well layer with gradually changed pressure, growing an InGaN well layer with gradually changed temperature, growing an InGaN well layer with simultaneously changed temperature and pressure, growing a high-temperature GaN barrier layer and growing an AlN layer. The method solves the problems of low quantum well growth quality and low quantum well radiation recombination efficiency in the conventional LED epitaxial growth method, thereby improving the luminous efficiency of the LED and reducing the warping of an epitaxial wafer.)

1. An LED epitaxial growth method is characterized by sequentially comprising the following steps: processing a substrate, growing a low-temperature buffer layer GaN, growing an undoped GaN layer, growing an N-type GaN layer doped with Si, growing a multi-quantum well layer, growing an AlGaN electronic barrier layer, growing a P-type GaN layer doped with Mg, and cooling; wherein growing the multiple quantum well layer sequentially comprises: the growth low-temperature GaN barrier layer, the InGaN well layer with gradually changed growth pressure, the InGaN well layer with gradually changed growth temperature and pressure, the high-temperature GaN barrier layer and the AlN layer are specifically as follows:

A. the pressure of the reaction chamber is controlled at 200-280mbar, the temperature of the reaction chamber is controlled at 500-580 ℃, and NH with the flow rate of 6000-8000sccm is introduced₃150-200sccm TMGa and 200-250L/min N₂Growing a low-temperature GaN barrier layer with the thickness of 5-8 nm;

B. the temperature of the reaction chamber is kept unchanged, the pressure of the reaction chamber is increased to 300mbar, and NH with the flow rate of 20000-₃200-300sccm TMGa and 1300-1400sccm TMIn, wherein the pressure of the reaction chamber is gradually increased from 300mbar to 350mbar in the growth process, and a pressure gradient InGaN well layer with the thickness of 10-20nm is grown;

C. keeping the pressure of the reaction chamber at 350mbar unchanged, raising the temperature of the reaction chamber to 800 ℃, and introducing NH with the flow rate of 20000-30000sccm₃200-300sccm TMGa and 1300-1400sccm TMIn, wherein the temperature of the reaction chamber is gradually reduced from 800 ℃ to 700 ℃ in the growth process, and a temperature gradient InGaN well layer with the thickness of 10-20nm is grown;

D. the pressure of the reaction chamber is increased to 550mbar, the temperature of the reaction chamber is increased to 900 ℃, NH with the flow rate of 20000-30000sccm is introduced₃200-300sccm TMGa and 1300-1400sccm TMIn, wherein the temperature of the reaction chamber is gradually increased from 900 ℃ to 1100 ℃ in the growth process, the pressure of the reaction chamber is gradually reduced from 550mbar to 500mbar, and an InGaN well layer is grown at the same time at a temperature and a pressure of 10-20 nm;

E. keeping the temperature of the reaction chamber unchanged at 1100 ℃, reducing the pressure of the reaction chamber to 350mbar when the pressure is reduced to 300-₃150-200sccm TMGa and 200-250L/min N₂And the mol ratio of nitrogen atoms to gallium atoms is gradually increased from 600:1 to 700:1, and a high-temperature GaN barrier layer with the thickness of 5-8nm is grown;

F. the temperature of the reaction chamber is reduced to 650-750 ℃, the pressure of the reaction chamber is increased to 400-450mbar, and N of 50-70sccm is introduced₂200, 250sccm TMAl and NH₃TMAl source is kept normally open during growth, and NH₃Alternately introducing NH into the reaction cavity in a pulse mode₃The interruption time and the introduction time of the AlN layer into the reaction cavity are respectively 12s and 6s, and the AlN layer with the thickness of 7nm to 10nm grows;

and repeating the steps A-F, and periodically and sequentially growing the low-temperature GaN barrier layer, the InGaN well layer with gradually changed pressure, the InGaN well layer with gradually changed temperature and pressure, the InGaN well layer with simultaneously gradually changed temperature and pressure, the high-temperature GaN barrier layer and the AlN layer, wherein the growth period number is 2-8.

2. The LED epitaxial growth method according to claim 1, characterized in that 100L/min-130L/min of H is introduced at a temperature of 1000 ℃ -1100 ℃₂And keeping the pressure of the reaction cavity at 100mbar-300mbar, and processing the sapphire substrate for 5min-10 min.

3. The LED epitaxial growth method according to claim 2, wherein the specific process for growing the low-temperature buffer layer GaN is as follows:

cooling to 500-600 deg.C, maintaining the pressure in the reaction chamber at 300-600mbar, and introducing NH with a flow rate of 10000-20000sccm₃TMGa of 50sccm-100sccm and H of 100L/min-130L/min₂Growing a low-temperature buffer layer GaN with the thickness of 20nm-40nm on a sapphire substrate;

raising the temperature to 1Keeping the pressure of the reaction cavity at 300mbar to 600mbar at 000 ℃ -1100 ℃, and introducing NH with the flow rate of 30000sccm to 40000sccm₃H of 100L/min-130L/min₂And preserving the heat for 300-500 s, and corroding the low-temperature buffer layer GaN into an irregular island shape.

4. The LED epitaxial growth method according to claim 1, wherein the specific process of growing the undoped GaN layer is as follows:

raising the temperature to 1000-1200 ℃, keeping the pressure of the reaction cavity at 300mbar-600mbar, and introducing NH with the flow rate of 30000sccm-40000sccm₃TMGa of 200sccm-400sccm and H of 100L/min-130L/min₂And continuously growing the undoped GaN layer of 2-4 mu m.

5. The LED epitaxial growth method according to claim 1, wherein the specific process for growing the Si-doped N-type GaN layer is as follows:

keeping the pressure of the reaction cavity at 300mbar-600mbar, keeping the temperature at 1000 ℃ -1200 ℃, and introducing NH with the flow rate of 30000sccm-60000sccm₃TMGa of 200sccm-400sccm, H of 100L/min-130L/min₂And 20sccm to 50sccm SiH₄Continuously growing N-type GaN doped with Si of 3 μm to 4 μm, wherein the doping concentration of Si is 5E18atoms/cm³-1E19atoms/cm³。

6. The LED epitaxial growth method according to claim 1, wherein the specific process for growing the AlGaN electron blocking layer is as follows:

introducing NH of 50000-70000sccm at the temperature of 900-950 ℃ and the pressure of the reaction chamber of 200-400mbar₃TMGa 30-60sccm, H100-130L/min₂100 TMAl with 130sccm, 1000 Cp with 1300sccm₂Growing the AlGaN electron barrier layer under the condition of Mg, wherein the thickness of the AlGaN layer is 40-60nm, and the Mg doping concentration is 1E19atoms/cm³-1E20atoms/cm³。

7. The LED epitaxial growth method according to claim 1, wherein the specific process for growing the Mg-doped P-type GaN layer is as follows:

keeping the pressure of the reaction cavity at 400mbar-900mbar and the temperature at 950-1000 ℃, and introducing NH with the flow rate of 50000sccm-70000sccm₃20sccm-100sccm of TMGa and 100L/min-130L/min of H₂And Cp of 1000sccm to 3000sccm₂Mg, continuously growing a P-type GaN layer doped with Mg with the concentration of 1E19atoms/cm and the thickness of 50nm-200nm³-1E20atoms/cm³。

8. The LED epitaxial growth method according to claim 1, wherein the specific cooling process comprises:

cooling to 650-680 ℃, preserving heat for 20-30min, closing the heating system and the gas supply system, and cooling along with the furnace.

Technical Field

The invention belongs to the technical field of LEDs, and particularly relates to an LED epitaxial growth method.

Background

A Light-Emitting Diode (LED) is a semiconductor electronic device that converts electrical energy into optical energy. When current flows through the LED, electrons and holes in the LED are recombined in the multiple quantum wells to emit monochromatic light. As a novel efficient, environment-friendly and green solid-state lighting source, the LED has the advantages of low voltage, low energy consumption, small size, light weight, long service life, high reliability, rich colors and the like. At present, the scale of domestic LED production is gradually enlarged, but the LED still has the problem of low luminous efficiency, and the energy-saving effect of the LED is influenced.

The LED epitaxial InGaN/GaN multi-quantum well prepared by the existing LED multi-quantum well growth method is not high in quality, the radiation efficiency of a light emitting region of the multi-quantum well is low, the improvement of the LED light emitting efficiency is seriously hindered, and the energy-saving effect of the LED is influenced. In addition, the problem of large epitaxial wafer warpage generally exists in the current 4-inch LED, and the reduction of the epitaxial wafer warpage is a technical problem in the industry.

In summary, there is a need for an LED epitaxial growth method to solve the problems of low light emitting efficiency and epitaxial wafer warpage in the conventional LED multiple quantum well.

Disclosure of Invention

The invention solves the problems of low quantum well growth quality and low quantum well radiation recombination efficiency in the existing LED epitaxial growth method by adopting a new multi-quantum well layer growth method, thereby improving the luminous efficiency of the LED, reducing the warpage of an epitaxial wafer and improving the yield of products.

The LED epitaxial growth method sequentially comprises the following steps: processing a substrate, growing a low-temperature buffer layer GaN, growing an undoped GaN layer, growing an N-type GaN layer doped with Si, growing a multi-quantum well layer, growing an AlGaN electronic barrier layer, growing a P-type GaN layer doped with Mg, and cooling; wherein growing the multiple quantum well layer sequentially comprises: the growth low-temperature GaN barrier layer, the InGaN well layer with gradually changed growth pressure, the InGaN well layer with gradually changed growth temperature and pressure, the high-temperature GaN barrier layer and the AlN layer are specifically as follows:

A. the pressure of the reaction cavity is controlled at 200-280mbar, the temperature of the reaction cavity is controlled at 500-580 ℃, and the flow rate is 60NH of 00-8000sccm₃150-200sccm TMGa and 200-250L/min N₂Growing a low-temperature GaN barrier layer with the thickness of 5-8 nm;

B. the temperature of the reaction chamber is kept unchanged, the pressure of the reaction chamber is increased to 300mbar, and NH with the flow rate of 20000-₃200-300sccm TMGa and 1300-1400sccm TMIn, wherein the pressure of the reaction chamber is gradually increased from 300mbar to 350mbar in the growth process, and a pressure gradient InGaN well layer with the thickness of 10-20nm is grown;

C. keeping the pressure of the reaction chamber at 350mbar unchanged, raising the temperature of the reaction chamber to 800 ℃, and introducing NH with the flow rate of 20000-30000sccm₃200-300sccm TMGa and 1300-1400sccm TMIn, wherein the temperature of the reaction chamber is gradually reduced from 800 ℃ to 700 ℃ in the growth process, and a temperature gradient InGaN well layer with the thickness of 10-20nm is grown;

D. the pressure of the reaction chamber is increased to 550mbar, the temperature of the reaction chamber is increased to 900 ℃, NH with the flow rate of 20000-30000sccm is introduced₃200-300sccm TMGa and 1300-1400sccm TMIn, wherein the temperature of the reaction chamber is gradually increased from 900 ℃ to 1100 ℃ in the growth process, the pressure of the reaction chamber is gradually reduced from 550mbar to 500mbar, and an InGaN well layer is grown at the same time at a temperature and a pressure of 10-20 nm;

E. keeping the temperature of the reaction chamber unchanged at 1100 ℃, reducing the pressure of the reaction chamber to 350mbar when the pressure is reduced to 300-₃150-200sccm TMGa and 200-250L/min N₂And the mol ratio of nitrogen atoms to gallium atoms is gradually increased from 600:1 to 700:1, and a high-temperature GaN barrier layer with the thickness of 5-8nm is grown;

F. the temperature of the reaction chamber is reduced to 650-750 ℃, the pressure of the reaction chamber is increased to 400-450mbar, and N of 50-70sccm is introduced₂200, 250sccm TMAl and NH₃TMAl source is kept normally open during growth, and NH₃Alternately introducing NH into the reaction cavity in a pulse mode₃The interruption time and the introduction time of the AlN layer into the reaction cavity are respectively 12s and 6s, and the AlN layer with the thickness of 7nm to 10nm grows;

and repeating the steps A-F, and periodically and sequentially growing the low-temperature GaN barrier layer, the InGaN well layer with gradually changed pressure, the InGaN well layer with gradually changed temperature and pressure, the InGaN well layer with simultaneously gradually changed temperature and pressure, the high-temperature GaN barrier layer and the AlN layer, wherein the growth period number is 2-8.

Preferably, the specific process for processing the substrate is as follows:

introducing H of 100L/min-130L/min at the temperature of 1000-1100 DEG C₂And keeping the pressure of the reaction cavity at 100mbar-300mbar, and processing the sapphire substrate for 5min-10 min.

Preferably, the specific process for growing the low-temperature buffer layer GaN is as follows:

cooling to 500-600 deg.C, maintaining the pressure in the reaction chamber at 300-600mbar, and introducing NH with a flow rate of 10000-20000sccm₃TMGa of 50sccm-100sccm and H of 100L/min-130L/min₂Growing a low-temperature buffer layer GaN with the thickness of 20nm-40nm on a sapphire substrate;

raising the temperature to 1000-1100 ℃, keeping the pressure of the reaction cavity at 300mbar-600mbar, and introducing NH with the flow rate of 30000sccm-40000sccm₃H of 100L/min-130L/min₂And preserving the heat for 300-500 s, and corroding the low-temperature buffer layer GaN into an irregular island shape.

Preferably, the specific process for growing the undoped GaN layer is as follows:

raising the temperature to 1000-1200 ℃, keeping the pressure of the reaction cavity at 300mbar-600mbar, and introducing NH with the flow rate of 30000sccm-40000sccm₃TMGa of 200sccm-400sccm and H of 100L/min-130L/min₂And continuously growing the undoped GaN layer of 2-4 mu m.

Preferably, the specific process for growing the doped GaN layer is as follows:

keeping the pressure of the reaction cavity at 300mbar-600mbar, keeping the temperature at 1000 ℃ -1200 ℃, and introducing NH with the flow rate of 30000sccm-60000sccm₃TMGa of 200sccm-400sccm, H of 100L/min-130L/min₂And 20sccm to 50sccm SiH₄Continuously growing N-type GaN doped with Si of 3 μm to 4 μm, wherein the doping concentration of Si is 5E18atoms/cm³-1E19atoms/cm³。

Preferably, the specific process for growing the AlGaN electron blocking layer is as follows:

introducing NH of 50000-70000sccm at the temperature of 900-950 ℃ and the pressure of the reaction chamber of 200-400mbar₃TMGa 30-60sccm, H100-130L/min₂100 TMAl with 130sccm, 1000 Cp with 1300sccm₂Growing the AlGaN electron barrier layer under the condition of Mg, wherein the thickness of the AlGaN layer is 40-60nm, and the Mg doping concentration is 1E19atoms/cm³-1E20atoms/cm³。

Preferably, the specific process for growing the Mg-doped P-type GaN layer is as follows:

keeping the pressure of the reaction cavity at 400mbar-900mbar and the temperature at 950-1000 ℃, and introducing NH with the flow rate of 50000sccm-70000sccm₃20sccm-100sccm of TMGa and 100L/min-130L/min of H₂And Cp of 1000sccm to 3000sccm₂Mg, continuously growing a P-type GaN layer doped with Mg with the concentration of 1E19atoms/cm and the thickness of 50nm-200nm³-1E20atoms/cm³。

Preferably, the specific process of cooling down is as follows:

cooling to 650-680 ℃, preserving heat for 20-30min, closing the heating system and the gas supply system, and cooling along with the furnace.

Compared with the traditional growth method, the LED epitaxial growth method provided by the invention achieves the following effects:

1. the AlN layer is inserted behind the quantum well GaN barrier layer, an effective potential barrier difference can be formed near the quantum well, and the potential barrier difference can inhibit holes in the quantum well from overflowing the quantum well, so that the hole concentration in the quantum well can be effectively improved, the recombination probability of electrons and holes is improved, and the LED light-emitting efficiency is improved. Growing AlN layer by controlling NH₃The growth mode can be gradually changed by alternately introducing the pulses, so that the sizes of crystal grains in the AlN thin film are gradually increased, the dislocation density is effectively reduced, the tensile stress in the growth process is reduced, and the generation of warping is avoided, thereby obtaining the epitaxial material with high crystal quality and good surface appearance.

2. According to the invention, the mol ratio of nitrogen atoms to gallium atoms is controlled to be gradually increased in the process of growing the high-temperature GaN barrier layer, the lattice matching degree between the InGaN layer/GaN layer and the GaN/AlN layer can be improved, and when the epitaxial material is continuously grown on the basis, the material reaches a completely relaxed state, so that the stress caused by lattice mismatch in the process of growing the LED epitaxial material is eliminated, the stress control window of the epitaxial film material is obviously increased, and the warping of an epitaxial wafer can be reduced.

3. By growing the InGaN well layer with the gradually changed pressure on the low-temperature GaN barrier layer, the InGaN well layer can be better matched with the GaN barrier layer, the lattice mismatch degree is smaller, epitaxial atoms can be uniformly filled upwards, and the uniformity in a chip is improved. Growing the InGaN well layer with the gradual temperature change on the InGaN well layer with the gradual pressure change, wherein the epitaxial layer atoms can release internal stress of the wafer to block upward extension of defects generated by lattice mismatch in the early stage. Growing temperature and pressure gradual change InGaN well layer simultaneously on temperature gradual change InGaN well layer, through pressure and growing temperature gradual change simultaneously, block once more that the direct parallel upwards passes the upwards extension of defect when passing, reduce dislocation density, improve crystal quality, LED's photoelectric properties such as luminous efficacy, forward voltage, antistatic yield obtain promoting by a wide margin.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention and not to limit the invention. In the drawings:

FIG. 1 is a schematic structural diagram of an LED epitaxy prepared by the method of the present invention;

FIG. 2 is a schematic structural diagram of an LED epitaxy prepared by a conventional method;

the light emitting diode comprises a sapphire substrate, a low-temperature GaN buffer layer, a non-doped GaN layer, a n-type GaN layer, a multi-quantum well light emitting layer, a low-temperature GaN barrier layer, a pressure gradient InGaN well layer, a temperature and pressure gradient InGaN well layer, a high-temperature GaN barrier layer, an AlN layer, a non-doped GaN layer_xGa_(1-x)N layer, 58 GaN layer, 6 AlGaN electron blocking layer, 7P type GaN.

Detailed Description

As used in the specification and in the claims, certain terms are used to refer to particular components. As one skilled in the art will appreciate, manufacturers may refer to a component by different names. This specification and claims do not intend to distinguish between components that differ in name but not function. In the following description and in the claims, the terms "include" and "comprise" are used in an open-ended fashion, and thus should be interpreted to mean "include, but not limited to. "substantially" means within an acceptable error range, and a person skilled in the art can solve the technical problem within a certain error range to substantially achieve the technical effect. The description which follows is a preferred embodiment of the present application, but is made for the purpose of illustrating the general principles of the application and not for the purpose of limiting the scope of the application. The protection scope of the present application shall be subject to the definitions of the appended claims.

Furthermore, the present description does not limit the components and method steps disclosed in the claims to those of the embodiments. In particular, the dimensions, materials, shapes, structural and adjacent orders, manufacturing methods, and the like of the components described in the embodiments are merely illustrative examples, and the scope of the present invention is not limited thereto, unless otherwise specified. The sizes and positional relationships of the structural members shown in the drawings are exaggerated for clarity of illustration.

The present application will be described in further detail below with reference to the accompanying drawings, but the present application is not limited thereto.