High-light-efficiency light-emitting diode epitaxial wafer growth methodTechnical Field
The invention belongs to the technical field of light-emitting diodes, and particularly relates to a high-light-efficiency light-emitting diode epitaxial wafer growth method.
Background
White light LEDs have now replaced traditional lighting, and become the first choice for general indoor and outdoor lighting. How to improve the luminous efficiency of a Light Emitting Diode (LED) is an important issue to be solved, and because of the properties of the material, structural defects such as dislocation, stacking fault, pore and the like are introduced into the epitaxial layer by mismatched stress, so that the quality of the crystal is deteriorated, thereby reducing the luminous efficiency, and how to improve the quality of the crystal with an epitaxial structure is an important issue to improve the luminous efficiency of the LED.
At present, the dislocation density of the LED epitaxial wafer can be well reduced through the PSS patterned substrate, and the luminous efficiency is improved. However, in the 3D process of actual growth, a small amount of GaN crystals are generated on the nonpolar surface of the Al2O3 and can be contacted with the GaN crystals grown on the C surface at the top end and below the substrate graph, so that the result is that 1. Because the polarities of two GaN are different, interface atoms are not easy to bond to generate new dislocation or the polarization effect is increased at the interface because of the different polarities of GaN, and 2. When the GaN crystals are filled and cover the top end of the substrate graph, holes can be formed in the substrate graph and the top end area thereof to influence the luminous efficiency.
Disclosure of Invention
In order to overcome the problems in the background technology, the invention develops a high-light-efficiency light-emitting diode epitaxial wafer growth method, which aims to eliminate non-C-plane generated GaN crystals by inserting a recrystallization layer into a 3D layer, crack the non-C-plane generated GaN crystals on a patterned substrate by the recrystallization layer, avoid or reduce the non-C-plane generated GaN crystals, reduce dislocation or polarization effect generated when different-polarity GaN crystals are bonded, maximally enable the GaN crystals generated on the C-plane to contact and bond at the top end of a substrate pattern, reduce the formation of cavities in the substrate pattern and the top end area thereof, reduce the generation of dislocation and improve the lattice quality of an epitaxial layer, thereby improving the luminous efficiency.
In order to achieve the above purpose, the invention adopts the following technical scheme:
A high-light-efficiency light-emitting diode epitaxial wafer growth method comprises the steps of growing a buffer layer on a substrate, growing a U-GaN 1 layer on the buffer layer, growing a U-GaN 2 layer on the buffer layer, growing an NGaN layer and an LED full-structure layer on the buffer layer, wherein the U-GaN 1 layer comprises a 3D1 layer which grows at a low temperature and a low growth speed, growing a recrystallization layer on the recrystallization layer, and growing a 3D2 layer on the recrystallization layer, wherein the temperature of the recrystallization layer is larger than that of the 3D1 layer, the NH3 flow rate of the recrystallization layer is smaller than that of the 3D1 layer, and the H2 flow rate is larger than that of the 3D1 layer.
Preferably, the 3D2R1 recrystallization layer and the 3D2R2 recrystallization layer are sequentially grown on the 3D1 layer, and the two recrystallization layers can quickly pull the temperature higher, so that better recrystallization is realized.
Preferably, the 3D1 layer growth conditions comprise 1030-1080 ℃ of temperature, 15-80 SLM of NH3, 25-100 SLM of N2, 120-350 SLM of H2, 160-500 Sccm of TMG, 0.03-0.09 mu m of growth thickness, 200-Torr of pressure P=and 700-900 RPM of rotation speed.
Preferably, in the 3D1 layer growth condition, NH3 accounts for 8% -15% of the total gas, N2 accounts for 15% -30% of the total gas, and H2 accounts for 50% -80%.
Preferably, the growth conditions of the recrystallization layer are 1080-1100 ℃, NH3 flow is smaller than 3D1, H2 flow is larger than 3D1, the recrystallization layer grows for 30 s-3 min under the condition of no Mo source, the pressure is P=200 Torr, the rotation speed is 700-900 RPM, and the recrystallization time is 10-300 s.
Preferably, the flow rate of NH3 in the recrystallization layer growth conditions comprises NH3 =0.
Preferably, the 3D2R1 recrystallization layer has a growth time of 10-60S and the 3D2R2 recrystallization layer has a growth time of 1-3 min.
Preferably, the 3D2R 1-3D 2R2 layer is grown for 5-10 times under the same condition in a circulating way, and the lattice quality is improved by repeatedly recrystallizing the non-C-plane GaN.
Preferably, the 3D2 layer growth conditions include 1080-1100 ℃ temperature, 15-80 SLM NH3 flow, 25-100 SLM N2 flow, 120-350 SLM H2 flow, 400-1600 Sccm TMG flow, 5-12 min growth, P=200 Torr pressure, 700-900 RPM rotation speed, and 3D2 layer growth atmosphere conditions similar to those of the 3D1 layer (high temperature, fast growth speed).
Preferably, in the 3D2 layer growth, NH3 accounts for 8% -15% of the total gas, N2 accounts for 15% -30% of the total gas, and H2 accounts for 50% -80% of the total gas.
Compared with the prior art, the invention has the following beneficial effects:
According to the invention, the GaN on the C surface/the non-C surface is decomposed by creatively utilizing different atmospheres of the recrystallization layer, so that the ratio of GaN crystals on the non-C surface is eliminated, the 3D2 growing speed is Wen Gaochang, mainly GaN crystals on the C surface are high, dislocation contacted with the non-C surface is eliminated, and the generation of voids is reduced in the GaN crystals growing on the top end of the patterned substrate, thereby improving the lattice quality of epitaxial materials and improving the luminous efficiency.
Drawings
FIG. 1 is a TEM image of a PSS patterned substrate and an actually grown U_GaN1 layer (3D layer) in the prior art.
Fig. 2 is a diagram showing the structure of an epitaxial wafer of a high-light-efficiency light-emitting diode according to the present invention.
FIG. 3 is a diagram of the epitaxial structure of the recrystallized layer of the present invention.
Fig. 4 is a diagram illustrating a process of the present invention.
Fig. 5 is a comparison of a TEM image of the actual growth with a SEM image of the 3D layer of the present invention.
Fig. 6 is a diagram illustrating a second embodiment of the present invention.
Fig. 7 is a graph comparing epitaxial wafer data grown with new and old epitaxial structures.
Detailed Description
In order to further describe the technical means and effects adopted by the present invention for achieving the intended purpose, the following detailed description will refer to the specific implementation, structure, characteristics and effects according to the present invention with reference to the accompanying drawings and preferred embodiments.
As shown in FIG. 1, in the actual growth 3D process of the existing growth method, a small amount of GaN crystals are generated on the nonpolar surface of Al2O3 and are in contact with the GaN crystals grown on the C surface at the top end and below of the substrate pattern, so that the result is that 1. Because the polarities of two GaN are different, interface atoms are not easy to bond to generate new dislocation or polarization effect is increased at the interface because of the polarity difference of GaN, 2. When the GaN crystals are filled and covered on the top end of the substrate pattern, holes can be formed in the substrate pattern and the top end area thereof to influence luminous efficiency (see 1-1 in particular FIG. 1), and 1-2 in FIG. 1 is a TEM image of an actually grown U_GaN1 layer (3D layer) which is basically consistent with the estimated growth.
The invention provides a high-light-efficiency light-emitting diode epitaxial wafer growth method which comprises the steps of growing a buffer layer on a substrate, growing a U-GaN 1 layer on the buffer layer, growing a U-GaN 2 layer on the buffer layer, and growing an NGaN layer and an LED full-structure layer on the buffer layer, wherein the U-GaN 1 layer comprises a 3D1 layer which grows at a low temperature and a low growth speed, growing a recrystallization layer on the recrystallization layer, and growing a 3D2 layer on the recrystallization layer, wherein the temperature of the recrystallization layer is higher than that of the 3D1 layer, the NH3 flow rate of the recrystallization layer is lower than that of the 3D1 layer, and the H2 flow rate is higher than that of the 3D1 layer.
As shown in fig. 3, in order that the temperature can be rapidly pulled up, better recrystallization is achieved, the recrystallized layer includes a 3D2R1 recrystallized layer and a 3D2R2 recrystallized layer, the 3D2R1 recrystallized layer is grown on the 3D1 layer, and the 3D2R2 recrystallized layer is grown on the 3D2R1 recrystallized layer. The flow rate of the NH3 of the 3D2R1/2 pause layer is smaller than that of the 3D1 layer, the flow rate of the H2 of the 3D2R1/2 pause layer is larger than that of the 3D1 layer, the temperature of the 3D2R1/2 is larger than that of the 3D1 layer by 30-50 ℃, and the growth thickness of the 3D1 layer is 0.03-0.09 mu m. And 3D 1-3D 2R2 is circularly grown, and non-C-plane grown GaN is repeatedly cracked and recrystallized, so that the non-C-plane GaN duty ratio is reduced, and the lattice quality of the whole epitaxial layer is improved.
Dislocation/stress generation and improvement process of GaN crystal on non-C-face and GaN crystal on C-face growth by recrystallization layer epitaxy structure:
The GaN growing on the buffer layer grows on the C surface, the polarity of the C surface is strong, gaN crystal nucleus is beneficial to crystallization, the growth speed of the GaN on the C surface is high, the proportion is high, the non-C surface is weaker due to the polarity, the growth speed of the generated GaN is slow, the proportion is low, and the GaN formed in two epitaxial modes has the problems of difficult bonding and large polarization effect due to different polarities, so that the lattice quality is influenced.
The growth conditions of the U_GaN1 layer are as follows:
embodiment one:
The 3D1 layer growth conditions comprise Temp 1030-1080 DEG, NH3 flow 15-80 SLM (NH3 accounts for 8-15% of total gas), N2 flow 25-100 SLM (N2 accounts for 15-30% of total gas), H2：120~350 SLM (H2 accounts for 50-80% of total gas), TMG flow 160-500 Sccm, growth thickness of 0.03-0.09 μm, pressure P=200 Torr, and rotation speed 700-900 RPM.
The growth condition of the 3D2R1/2 recrystallization layer is Temp 1080-1100 ℃, the NH3 flow is smaller than 3D1 (including NH3=0), H2 flow is larger than 3D1, the growth is carried out for 30 s-3 min under the condition of no Mo source being introduced, the pressure P=200 Torr, the rotating speed is 700-900 RPM, and the recrystallization time is 10-300 s.
The 3D2 layer growth conditions include Temp 1080-1100 ℃, NH3 flow 15-80 SLM (NH3 accounts for 8% -15% of total gas), N2：25~100SLM(N2 accounts for 15% -30% of total gas), H2 flow 120-350 SLM (H2 accounts for 50% -80% of total gas), TMG flow 400-1600 Sccm for 5-12 min under pressure P=200 Torr, rotation speed 700-900 RPM, and 3D2 layer growth atmosphere conditions identical to those of the 3D1 layer (high temperature, long speed).
And (3) circularly growing the 3D 1-3D 2R layer for 5-loop times under the same condition, and repeatedly recrystallizing the non-C-surface GaN to improve the lattice quality.
Embodiment two:
The 3D1 layer growth conditions comprise Temp 1030 degrees, NH3 flow rate of 15-80 SLM (NH3 accounts for 8% -15% of total gas), N2 flow rate of 25-100 SLM (N2 accounts for 15% -30% of total gas), H2 flow rate of 120-350 SLM (H2 accounts for 50% -80% of total gas), TMG flow rate of 160-500 Sccm, growth thickness of 0.03-0.09 mu m, pressure P=200 Torr, rotation speed of 700-900 RPM, and each cycle temperature of the 3D1 layer is 5-10 (Temp 1035-1070 degrees) higher than the previous cycle temperature until the last cycle temperature is 1080 degrees.
The 3D2R1/2 recrystallization layer growing conditions comprise Temp of 1080-1100 ℃, NH3 flow of A (wherein A is less than 3D1 NH3 flow), H2 flow of B (wherein B is more than 3D 1H2 flow), pressure P=200 Torr for 30 s-3 min under the condition of no Mo source inlet, rotating speed of 700-900 RPM, recrystallization time of 10-300 s, wherein each cycle growth temperature is different from the previous cycle temperature (the temperature of the recrystallization layer is 30-50 degrees higher than the temperature of the 3D1 layer), each cycle growth air volume is different from the previous cycle (the NH3 flow inlet amount of the recrystallization layer is less than 3D1, and H2 flow inlet amount is more than 3D1 and comprises one or more cycles of NH3 =0).
The 3D2 layer growth conditions include Temp 1080-1100 ℃, NH3 flow 15-80 SLM (NH3 accounts for 8% -15% of total gas), N2 flow 25-100 SLM (N2 accounts for 15% -30% of total gas), H2 flow 120-350 SLM (H2 accounts for 50% -80% of total gas), TMG flow 400-1600 Sccm growth 5-12 min pressure P=200 Torr, rotation speed 700-900 RPM, and 3D2 growth atmosphere conditions same as 3D1 (high temperature, long speed).
The 3D 1-3D 2R layer is grown for 5-10 times in a circulating way, wherein the temperature of the 3D1 layer is 5 degrees higher than that of the previous cycle in each circulating way, and the temperature of the 3D1 layer is recrystallized in each circulating way. See fig. 6 for an illustration of 3 cycles.
According to the invention, through epitaxial wafers grown on the same substrate and the same machine table and in new and old epitaxial structures, PL data tests show that XRD data 002/102 of the new structure are obviously reduced, and the crystal lattice quality of the new structure growth is better, so that the purpose of finally improving the light efficiency is achieved, and specific data are shown in figure 7.
The present invention is not limited in any way by the above-described preferred embodiments, but is not limited to the above-described preferred embodiments, and any person skilled in the art will appreciate that the present invention can be embodied in the form of a program for carrying out the method of the present invention, while the above disclosure is directed to equivalent embodiments capable of being modified or altered in some ways, it is apparent that any modifications, equivalent variations and alterations made to the above embodiments according to the technical principles of the present invention fall within the scope of the present invention.