Ultraviolet led epitaxial wafer, epitaxial growth method and ultraviolet led chip

Abstract

The application provides an ultraviolet LED epitaxial wafer, an epitaxial growth method and an ultraviolet LED chip. The epitaxial growth method comprises the following steps: when a multi-quantum well layer is grown, a well layer is first grown; when the growth of the well layer is completed, TMIn is introduced to react with NH3 to generate InN; the InN is decomposed into In quantum dots at high temperature; and when the In quantum dots are distributed in the well layer, a barrier layer is grown. The well layer is a GaN layer, the barrier layer is an AlGaN layer, and the GaN layer, the In quantum dots and the AlGaN layer are grown periodically. Since the multi-quantum well layer contains In light-emitting quantum dots, and the In light-emitting quantum dots have no actual thickness, the light-emitting efficiency of the ultraviolet LED is improved without affecting the light-emitting wavelength of the ultraviolet LED.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of LED, in particular to a UV LED epitaxial wafer, an epitaxial growth method and a UV LED chip. BACKGROUND

[0002] In the past decade, AlGaN material has attracted much attention due to its great application potential in UV optoelectronic devices. UV LED has the characteristics of high photon energy, short wavelength, small volume, low power consumption, long service life, environmental friendliness and the like, and has wide application in high color rendering index white light illumination, high-density optical data storage, sensors, lithography, air purification and environmental protection.

[0003] However, the development of AlGaN-based UV LED faces many technical difficulties, of which the relatively low quantum efficiency of AlGaN-based UV LED compared with blue-green light emitting diode is worth paying attention to, which seriously limits the performance of UV light emitting diode. In order to improve the quantum efficiency of UV LED, high-conductivity p-type and n-type AlGaN materials, high-crystal-quality epitaxial layers and high-internal-quantum-efficiency quantum well structures are needed, which undoubtedly increases the process difficulty and cost.

[0004] At present, the main reason why the internal quantum efficiency of AlGaN-based UV LED is relatively low compared with blue-green light emitting diode is that the blue-green light LED quantum well is composed of InGaN / GaN, which is easy to form In-rich light-emitting quantum dots in the quantum well, thereby improving the light-emitting efficiency. Since the wavelength of UV LED is relatively short, the quantum well needs to be composed of GaN / AlGaN or AlGaN / AlGaN. It can be found that the quantum well lacks In-rich light-emitting quantum dots, resulting in low light-emitting efficiency. SUMMARY

[0005] Based on this, the purpose of the present application is to provide a UV LED epitaxial wafer, an epitaxial growth method and a UV LED chip, which can improve the light-emitting efficiency without affecting the light-emitting wavelength of the UV LED.

[0006] According to an epitaxial growth method of a UV LED epitaxial wafer in an embodiment of the present application, the epitaxial growth method comprises:

[0007] When growing a multi-quantum well layer, a well layer is first grown, and when the growth of the well layer is completed, TMIn is introduced to react with NH3 to generate InN, and the InN is decomposed into In quantum dots at high temperature. When the In quantum dots are distributed in the well layer, a barrier layer is grown, wherein the well layer is a GaN layer, the barrier layer is an AlGaN layer, and the GaN layer, the In quantum dots and the AlGaN layer are grown periodically.

[0008] Preferably, the epitaxial growth method further comprises:

[0009] providing a sapphire substrate required for growth;

[0010] sequentially epitaxially growing an AlN buffer layer, an undoped AlGaN layer, an N-type doped AlGaN layer, the multi-quantum well layer, an electron blocking layer, a P-type doped GaN layer and a contact layer on the sapphire substrate.

[0011] Preferably, the growth temperature of the GaN layer is 900-1000℃, the growth pressure is 50-200 torr, the flow rate of the TMIn introduced after the growth of the GaN layer in a single cycle is 100-800 sccm, the introduction time of the TMIn in a single cycle is 10-60 s, the generation temperature of the In quantum dots is 1000-1100℃, the pressure is 50-100 torr, and the growth temperature of the AlGaN layer is 1000-1100℃, the growth pressure is 50-100 torr, and the Al component is 0.1-0.5.

[0012] Preferably, the growth temperature of the electron blocking layer is 1000-1100℃, and the growth pressure is 50-100 torr.

[0013] Preferably, the growth temperature of the N-type doped AlGaN layer is 1100-1200℃, and the growth pressure is 50-100 torr, the N-type doped AlGaN layer is doped with Si, and the doping concentration of the Si is 10 19 cm -3 -10 20 cm -3 , and the Al component is 0.2-0.6.

[0014] According to one of the embodiments of the present application, an ultraviolet LED epitaxial wafer is prepared by the epitaxial growth method of the LED epitaxial wafer described above, and comprises a multi-quantum well layer, the multi-quantum well layer is a periodic structure alternately grown by a well layer containing In quantum dots and a barrier layer, the well layer is a GaN layer, and the barrier layer is an AlGaN layer.

[0015] Preferably, the thickness of the GaN layer in a single cycle is 2-4 nm, and the thickness of the AlGaN layer in a single cycle is 8-20 nm.

[0016] Preferably, the ultraviolet LED epitaxial wafer further comprises a sapphire substrate, an AlN buffer layer, an undoped AlGaN layer, an N-type doped AlGaN layer, an electron blocking layer, a P-type doped GaN layer and a contact layer.

[0017] The AlN buffer layer, the undoped AlGaN layer, the N-type doped AlGaN layer, the multi-quantum well layer, the electron blocking layer, the P-type doped GaN layer and the contact layer are epitaxially grown on the sapphire substrate in sequence.

[0018] Preferably, the thickness of the AlN buffer layer is 15-50 nm, the thickness of the undoped AlGaN layer is 1-3 μm, the thickness of the N-type doped AlGaN layer is 1-3 μm, the thickness of the multi-quantum well layer is 50-288 nm, the thickness of the electron blocking layer is 20-100 nm, the thickness of the P-type GaN layer is 30-200 nm, and the thickness of the contact layer is 10-50 nm.

[0019] Preferably, the electron blocking layer and the contact layer are both AlGaN layers.

[0020] According to one of the embodiments of the present application, the ultraviolet LED chip comprises the above ultraviolet LED epitaxial wafer.

[0021] Compared with the prior art, by changing the multi-quantum well layer structure, In quantum dots are distributed in the GaN layer to form a multi-quantum well layer structure of GaN layer / AlGaN layer containing In quantum dots, specifically, InN is generated by the reaction of TMIn and NH3, and the InN is decomposed into In light-emitting quantum dots in a high-temperature environment and distributed in the GaN well layer. The In quantum dots in the multi-quantum well layer structure actually have no thickness, so they will not affect the light-emitting wavelength of the ultraviolet LED. The In light-emitting quantum dots generated by decomposition can improve the internal quantum effect of the ultraviolet LED, thereby achieving the effect of improving the light-emitting efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 Fig. 1 is a structural schematic diagram of the LED epitaxial wafer in the first embodiment of the present application;

[0023] Figure 2 Fig. 2 is a flow chart of the epitaxial growth method of the LED epitaxial wafer in the second embodiment of the present application. DETAILED DESCRIPTION

[0024] In order to facilitate the understanding of the present application, the present application will be described more fully below with reference to the related drawings. Several embodiments of the present application are shown in the drawings. However, the present application can be realized in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive.

[0025] It should be noted that when an element as a means plus function is claimed, where the term "is" is used, it should be interpreted as consists of rather than consists exclusively of. When the term "comprises" is used, it is to be interpreted as comprising, consisting of, absorbing, accounting for, pertaining to, etc. It should be noted that when an element is claimed as "means plus function", it should not be construed to be directed to the broader function, but to the structure described by the means plus function element.

[0026] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description herein is for describing particular embodiments only and is not intended to be limiting of the application. The use herein of the terms "including", "comprising", "having" and the like are specifically intended to be interpreted as "including but not limited to".

[0027] Embodiment One

[0028] Referring to Figure 1 , an ultraviolet LED epitaxial wafer in the embodiment one of the present application is shown, which comprises a sapphire substrate 10, and an AlN buffer layer 20, an undoped AlGaN layer 30, an N-type doped AlGaN layer 40, a multi-quantum well layer 50, an electron blocking layer 60, a P-type doped GaN layer 70 and a contact layer 80 which are epitaxially grown on the sapphire substrate 10 in sequence.

[0029] In the embodiment, the multi-quantum well layer 50 is a periodic structure which is alternately grown by a well layer containing In quantum dots and a barrier layer, wherein the well layer is a GaN layer, the thickness of a single period GaN layer is 2-4 nm, the barrier layer is an AlGaN layer, the thickness of a single period AlGaN layer is 8-20 nm, and it should be noted that the In quantum dots are formed by the reaction of TMIn and NH3 and high-temperature decomposition, and it can be understood that, since the growth process of the epitaxial layer such as the well layer is generally from one side of the substrate to the opposite side, the In component in the In quantum dot formation process can be controlled, and then the GaN well layer containing In quantum dots with gradually increasing In component is prepared.

[0030] For example but not limitation, in some preferable embodiments of the present embodiment, the thickness of the AlN buffer layer 20 is 15 nm to 50 nm, such as 20 nm, 25 nm, 30 nm, etc.; the thickness of the undoped AlGaN layer 30 is 1 μm to 3 μm, such as 1 μm, 2 μm, 3 μm, etc.; the thickness of the N-type doped AlGaN layer 40 is 1 μm to 3 μm, such as 1 μm, 2 μm, 3 μm, etc.; the thickness of the multi-quantum well layer 50 is 50 nm to 288 nm, such as 100 nm, 150 nm, 200 nm, etc.; the thickness of the electron blocking layer 60 is 20 nm to 100 nm, such as 30 nm, 40 nm, 50 nm, etc.; the thickness of the P-type GaN layer 70 is 30 nm to 200 nm, such as 50 nm, 100 nm, 150 nm, etc.; and the thickness of the contact layer 80 is 10 nm to 50 nm, such as 20 nm, 30 nm, 40 nm, etc.

[0031] Specifically, the multi-quantum well layer 50 comprises GaN well layers and AlGaN barrier layers, and is a periodic structure alternately grown by GaN well layers and AlGaN barrier layers. For example but not limitation, in some preferable embodiments of the present embodiment, the thickness of a single period GaN layer is 2 nm to 4 nm, such as 2 nm, 3 nm, 4 nm, etc.; and the thickness of a single period AlGaN layer is 8 nm to 20 nm, such as 10 nm, 12 nm, 14 nm, etc. The alternating period of GaN well layers and AlGaN barrier layers in the multi-quantum well layer 50 is 5 to 12, such as 9, i.e. the multi-quantum well layer 50 is grown by 9 layers in total.

[0032] Embodiment Two

[0033] Please refer to Figure 2 , which shows an epitaxial growth method of an ultraviolet LED epitaxial wafer according to Embodiment Two of the present application, for preparing the ultraviolet LED epitaxial wafer in Embodiment One. The method specifically comprises steps S201 to S209, wherein:

[0034] Step S201, providing a sapphire substrate required for growth.

[0035] Step S202, growing an AlN buffer layer, with a growth thickness of 15 nm to 50 nm.

[0036] In the present embodiment, the AlN buffer layer is deposited in an application material PVD, with a growth temperature of 400 ℃ to 650 ℃, a sputtering power of 2000 W to 4000 W, and a pressure of 1 torr to 10 torr.

[0037] Step S203, growing an undoped AlGaN layer, with a growth thickness of 1 μm to 3 μm.

[0038] Specifically, after annealing, the temperature is adjusted to 1050-1200℃, the growth pressure is 50-100 torr, and the Al component is 0.3-0.8.

[0039] In step S204, an N-type doped AlGaN layer is grown, with a growth thickness of 1-3 μm.

[0040] It should be noted that after the undoped AlGaN layer is grown, an N-type Si-doped AlGaN layer is grown on the undoped AlGaN layer, with a growth temperature of 1100-1200℃, a growth pressure of 50-100 torr, and a Si doping concentration of 10 19 cm -3 -10 20 cm -3 , and an Al component of 0.2-0.6.

[0041] In step S205, a multi-quantum well layer is grown, with a growth thickness of 50-288 nm.

[0042] In this embodiment, the multi-quantum well layer (MQW) is composed of 5-12 periods of GaN / AlGaN, with GaN as the well layer and AlGaN as the barrier layer. It should be noted that the GaN well layer contains In quantum dots. Specifically, the GaN layer is grown at a temperature of 900-1000℃ and a pressure of 50-200 torr. After the GaN layer in a single period is grown, TMIn is introduced, with a flow rate of 100-800 sccm and an introduction time of 10-60 s. The In quantum dots are generated at a temperature of 1000-1100℃ and a pressure of 50-100 torr. The AlGaN layer is grown at a temperature of 1000-1100℃ and a pressure of 50-100 torr, with an Al component of 0.1-0.5.

[0043] In this embodiment, trimethylaluminum (TMAl), trimethylgallium or triethylgallium (TMGa or TEGa), and NH3 are used as precursors of the group III and group V sources, respectively, and silane and dimethyl magnesium are used as precursors of the N-type and P-type dopants, respectively. N2 and H2 are used as carrier gases. When TMIn is introduced, it reacts with NH3 to form InN, which is easily decomposed at high temperatures and cannot form a film. Therefore, the thickness of the InN film does not exist in practice, and thus does not affect the emission wavelength of the UV LED. The decomposition of InN provides In quantum dots, which are distributed in the GaN well layer, thereby forming In-rich light-emitting quantum dots in the quantum well, achieving the purpose of improving the light-emitting efficiency.

[0044] In step S206, an electron blocking layer is grown, with a growth thickness of 20-100 nm.

[0045] In the embodiment, the electron blocking layer is an AlGaN layer, the growth temperature is 1000-1100 DEG C, the growth pressure is 50-100 torr, and the Al component is 0.1-0.5.

[0046] In step S207, a P-type GaN layer is grown, with a growth thickness of 30-200 nm.

[0047] Specifically, the P-type GaN layer is a Mg-doped GaN layer, with a Mg doping concentration of 10 19 cm -3 -10 20 cm -3 , the growth temperature is 900-1000 DEG C, and the growth pressure is 50-100 torr.

[0048] In step S208, a contact layer is grown, with a growth thickness of 10-50 nm.

[0049] The contact layer is an AlGaN layer, the growth temperature is 1000-1100 DEG C, the growth pressure is 50-100 torr, and the Al component is 0.0-0.3.

[0050] In step S209, annealing is performed in N2.

[0051] It should be noted that after the epitaxial structure growth is completed, the reaction cavity temperature is reduced, and annealing is performed in an N2 atmosphere, with an annealing temperature of 650-850 DEG C and an annealing time of 5-15 min, and the epitaxial growth is completed when the reaction cavity temperature reaches room temperature.

[0052] In summary, the ultraviolet LED epitaxial wafer and the epitaxial growth method of the embodiment can improve the light-emitting efficiency by changing the multi-quantum well layer structure, distributing In quantum dots in the GaN layer, forming a multi-quantum well layer structure of GaN layer / AlGaN layer containing In quantum dots, and specifically, InN is generated by the reaction of TMIn and NH3, the InN decomposes into In light-emitting quantum dots in a high-temperature environment, and the In quantum dots in the multi-quantum well layer structure do not actually have a thickness, so they do not affect the light-emitting wavelength of the ultraviolet LED, and the In light-emitting quantum dots generated by decomposition can improve the internal quantum effect of the ultraviolet LED, thereby achieving the effect of improving the light-emitting efficiency.

[0053] Embodiment Three

[0054] The embodiment three provides an ultraviolet LED chip, which comprises the ultraviolet LED epitaxial wafer in the above embodiment one, and the ultraviolet LED epitaxial wafer can be obtained by the epitaxial growth method of the ultraviolet LED epitaxial wafer in the above embodiment two.

[0055] The above embodiments only express several implementation manners of the present application, which are described in a more specific and detailed manner, but cannot be understood as a limitation on the patent scope of the present application. It should be noted that, for ordinary skilled persons in the art, several modifications and improvements can be made without departing from the concept of the present application, which all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. A method for epitaxial growth of ultraviolet LED epitaxial wafers, characterized in that, The epitaxial growth method includes: In the growth of a multi-quantum-well layer, the well layer is first grown. After the well layer growth is completed, TMIn is introduced and reacts with NH3 to generate InN. The InN is decomposed into In quantum dots at high temperature. After the In quantum dots are distributed in the well layer, a barrier layer is grown. The well layer is a GaN layer and the barrier layer is an AlGaN layer. The GaN layer, the In quantum dots and the AlGaN layer are grown sequentially and periodically. The epitaxial growth method further includes: Provide a sapphire substrate required for growth; An AlN buffer layer, an undoped AlGaN layer, an N-type doped AlGaN layer, a multi-quantum well layer, an electron blocking layer, a P-type doped GaN layer, and a contact layer are epitaxially grown sequentially on the sapphire substrate. The GaN layer is grown at a temperature of 900℃ to 1000℃ and a growth pressure of 50 torr to 200 torr. After the GaN layer growth is completed in a single cycle, the flow rate of the TMIn is 100 sccm to 800 sccm, and the TMIn introduction time in a single cycle is 10 s to 60 s. The In quantum formation temperature is 1000℃ to 1100℃ and the pressure is 50 torr to 100 torr. The AlGaN layer is grown at a temperature of 1000℃ to 1100℃ and a growth pressure of 50 torr to 100 torr. The Al composition is 0.1% to 0.5%.

2. The epitaxial growth method for ultraviolet LED epitaxial wafers according to claim 1, characterized in that, The electron blocking layer is grown at a temperature of 1000℃ to 1100℃ and a growth pressure of 50 torr to 100 torr.

3. The epitaxial growth method for ultraviolet LED epitaxial wafers according to claim 1, characterized in that, The N-type doped AlGaN layer is grown at a temperature of 1100℃ to 1200℃ and a growth pressure of 50 torr to 100 torr. The N-type doped AlGaN layer is doped with Si at a doping concentration of 10%. 19 cm -3 ~10 20 cm -3 The Al component is 0.2–0.6%.

4. A UV LED epitaxial wafer, prepared by the epitaxial growth method for LED epitaxial wafers according to any one of claims 1-3, characterized in that, It includes a multi-quantum well layer, which is a periodic structure formed by alternating well layers and barrier layers containing In quantum dots, wherein the well layers are GaN layers and the barrier layers are AlGaN layers; The thickness of the GaN layer in a single period is 2nm to 4nm, and the thickness of the AlGaN layer in a single period is 8nm to 20nm.

5. The ultraviolet LED epitaxial wafer according to claim 4, characterized in that, The ultraviolet LED epitaxial wafer also includes a sapphire substrate, an AlN buffer layer, an undoped AlGaN layer, an N-type doped AlGaN layer, an electron blocking layer, a P-type doped GaN layer, and a contact layer. The AlN buffer layer, the undoped AlGaN layer, the N-type doped AlGaN layer, the multiple quantum well layer, the electron blocking layer, the P-type doped GaN layer, and the contact layer are sequentially epitaxially grown on the sapphire substrate.

6. The ultraviolet LED epitaxial wafer according to claim 5, characterized in that, The thickness of the AlN buffer layer is 15nm to 50nm, the thickness of the undoped AlGaN layer is 1μm to 3μm, the thickness of the N-type doped AlGaN layer is 1μm to 3μm, the thickness of the multiple quantum well layer is 50nm to 288nm, the thickness of the electron blocking layer is 20nm to 100nm, the thickness of the P-type doped GaN layer is 30nm to 200nm, and the thickness of the contact layer is 10nm to 50nm.

7. The ultraviolet LED epitaxial wafer according to claim 6, characterized in that, Both the electron blocking layer and the contact layer are AlGaN layers.

8. A UV LED chip, characterized in that, Includes the ultraviolet LED epitaxial wafer as described in any one of claims 4-7.

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