阅读说明：本技术 一种深紫外led外延结构及其制备方法 (Deep ultraviolet LED epitaxial structure and preparation method thereof ) 是由 齐胜利 郭丽彬 刘亚柱 于 2021-01-04 设计创作，主要内容包括：本发明属于半导体光电子器件技术领域中的深紫外LED外延生长技术,具体涉及一种深紫外LED外延结构及其制备方法。所述深紫外LED外延结构从下而上由衬底、高温AlN层、N型AlGaN层、MQW多量子阱发光层、P型GaN层组成,所述N型AlGaN层上开设有V型状缺陷阵列,MQW多量子阱发光层、P型GaN层在N型AlGaN层上的V型状缺陷上依次继续外延生长。本发明通过在N型AlGaN层刻蚀出V型缺陷,使得MQW在非极性面上生长,释放生长过程中产生的应力,V型缺陷坑使得有源发光区由传统的平面结构变为立体结构,增加了水平的PN结,可控制载流子输运路径,增加复合面积,增加UVCLED的发光面积,提高发光亮度,解决了现有技术中深紫外LED器件的发光效率偏低的问题。(The invention belongs to a deep ultraviolet LED epitaxial growth technology in the technical field of semiconductor optoelectronic devices, and particularly relates to a deep ultraviolet LED epitaxial structure and a preparation method thereof. The deep ultraviolet LED epitaxial structure comprises a substrate, a high-temperature AlN layer, an N-type AlGaN layer, an MQW multi-quantum well luminescent layer and a P-type GaN layer from bottom to top, wherein a V-shaped defect array is arranged on the N-type AlGaN layer, and the MQW multi-quantum well luminescent layer and the P-type GaN layer continue epitaxial growth on the V-shaped defects on the N-type AlGaN layer in sequence. According to the invention, the V-shaped defects are etched on the N-shaped AlGaN layer, so that the MQW grows on a non-polar surface, the stress generated in the growth process is released, the active light emitting region is changed into a three-dimensional structure from a traditional planar structure by the V-shaped defect pits, the horizontal PN junction is increased, a carrier transport path can be controlled, the composite area is increased, the light emitting area of the UVCLED is increased, the light emitting brightness is improved, and the problem that the light emitting efficiency of a deep ultraviolet LED device in the prior art is low is solved.)

1. The deep ultraviolet LED epitaxial structure is characterized by sequentially comprising a substrate (1), a high-temperature AlN layer (2), an N-type AlGaN layer (3), an MQW multi-quantum well luminescent layer (4) and a P-type GaN layer (5) from bottom to top, wherein the N-type AlGaN layer (3) is an N-type AlGaN layer provided with a V-shaped defect array, and the MQW multi-quantum well luminescent layer (4) and the P-type GaN layer (5) are epitaxially grown on the surface of the V-shaped defect array on the N-type AlGaN layer (3) in sequence.

2. The deep ultraviolet LED epitaxial structure of claim 1, wherein an N-type AlGaN cladding layer (6) is arranged between the N-type AlGaN layer (3) and the MQW multi-quantum well light-emitting layer (4), the thickness of the N-type AlGaN cladding layer (6) is 200-1000nm, and the content of Al component is 50-80 wt%.

3. The deep ultraviolet LED epitaxy structure according to claim 1, characterised in that the MQW multiple quantum well light-emitting layer (4) is made of quantum barrier layer Al_xGa_1-xN and quantum well layer Al_yGa_1-yN grows alternately in turn, wherein 45 percent of the total weight of the N<x<60％、35％<y<50 percent, one quantum barrier layer and one quantum well layer form a growth cycle, and the cycle number is 3-6.

4. Deep ultraviolet LED epitaxy structure according to claim 1, characterized in that the substrate (1) is a sapphire flat sheet substrate or a nano-scale patterned substrate sheet, NPSS substrate.

5. The deep ultraviolet LED epitaxy structure according to claim 1, characterised in that the high temperature AlN layer (2) is 1.5-5um thick.

6. Deep ultraviolet LED epitaxy structure according to claim 1, characterised in that the thickness of the N-type AlGaN layer (3)0.5-3um, and Si doping concentration in the layer is 1 × 10¹⁷/cm³-9×10¹⁸/cm³And the Al component is 40-80 wt%.

7. The deep ultraviolet LED epitaxial structure according to claim 1, wherein the V-shaped defect array is composed of a plurality of V-shaped defects distributed at intervals, and the opening size of the V-shaped defects is 90-200nm and the depth is 90-150 nm.

8. Deep ultraviolet LED epitaxy structure according to claim 1, characterised in that the thickness of the MQW multiple quantum well light-emitting layer (4) is between 15 and 100 nm.

9. The deep ultraviolet LED epitaxial structure according to claim 1, characterized in that the thickness of the P-type GaN layer (5) is 50-300nm, and the doping concentration of Mg in this layer is greater than 1 x 10¹⁸/cm³。

10. A method for preparing a deep ultraviolet LED epitaxial structure according to any one of claims 1 to 9, comprising the steps of:

s1, the temperature of the reaction chamber is 1200-1400 ℃, and a high-temperature AlN layer (2) is epitaxially grown on the substrate (1);

s2, growing an N-type AlGaN layer (3) on the high-temperature AlN layer (2);

s3, etching the N-type AlGaN layer (3) to form a V-shaped defect array;

s4, growing an MQW multi-quantum well light-emitting layer (4) on the surface of the N-type AlGaN layer (3) where the V-shaped defect array is located;

s5, growing a P-type GaN layer (5) after the MQW multi-quantum well light-emitting layer (4) finishes growing;

and S6, after the epitaxial growth is finished, reducing the temperature of the reaction chamber to between 450 and 800 ℃, annealing for 2-20min in a pure nitrogen atmosphere, and then reducing the temperature to room temperature to obtain the deep ultraviolet LED epitaxial structure.

11. The method of claim 10, wherein Ga is derived from trimethylgallium and triethylgallium, Al is derived from trimethylaluminum, N is derived from ammonia, silane is used as an N-type dopant, and magnesium dicylocene is used as a p-type dopant in each layer.

Technical Field

The invention belongs to a deep ultraviolet LED epitaxial growth technology in the technical field of semiconductor optoelectronic devices, and particularly relates to a deep ultraviolet LED epitaxial structure and a preparation method thereof.

Background

The AlGaN-based semiconductor deep ultraviolet LED has great application value and wide market space in the aspects of high-density optical storage, white light illumination, printing, sterilization, disinfection, air and water purification, non-line-of-sight military secret communication, biochemistry, medical diagnosis and the like. In recent years, AlGaN-based deep ultraviolet LEDs have attracted much attention by researchers and industries, and have been greatly developed and advanced, however, the main problem that limits further development of AlGaN-based deep ultraviolet LEDs is the problem of luminous efficiency, and for deep ultraviolet devices, the electro-optic conversion efficiency is generally below 5%. To achieve efficiency values far above this, necessary changes to the structure of the device are required.

The light-emitting efficiency of the deep ultraviolet LED is influenced by an MQW structure, P layer Mg doping and defect control, but in the current situation, the expected effect is not obtained by improving the light-emitting efficiency in the aspects. It is reported in the industry that when WPE of UVCLED can reach 5%, more scenario applications will be turned on.

Disclosure of Invention

The invention provides a deep ultraviolet LED epitaxial structure and a preparation method thereof, aiming at overcoming the defect of low luminous efficiency of a deep ultraviolet LED in the prior art.

In order to solve the technical problem, the technical scheme is that the deep ultraviolet LED epitaxial structure sequentially comprises a substrate, a high-temperature AlN layer, an N-type AlGaN layer, an MQW multi-quantum well light-emitting layer and a P-type GaN layer from bottom to top, wherein the N-type AlGaN layer is an N-type AlGaN layer provided with a V-shaped defect array, and the MQW multi-quantum well light-emitting layer and the P-type GaN layer are sequentially epitaxially grown on the surface of the N-type AlGaN layer where the V-shaped defect array is located.

As a further improvement of the deep ultraviolet LED epitaxial structure:

preferably, an N-type AlGaN covering layer is arranged between the N-type AlGaN layer and the MQW multiple quantum well light-emitting layer, the thickness of the N-type AlGaN covering layer is 200-1000nm, and the content of the Al component is 50-80 wt%.

Preferably, the first and second liquid crystal materials are,the MQW multi-quantum well luminescent layer is composed of a quantum barrier layer Al_xGa_1-xN and quantum well layer Al_yGa_1-yN grows alternately in turn, wherein 45 percent of the total weight of the N<x<60％、35％<y<50 percent, one quantum barrier layer and one quantum well layer form a growth cycle, and the cycle number is 3-6.

Preferably, the substrate is a sapphire flat sheet substrate or a nano-scale patterned substrate sheet, i.e. an NPSS substrate.

Preferably, the thickness of the high-temperature AlN layer is 1.5-5 um.

Preferably, the thickness of the N-type AlGaN layer is 0.5-3um, and the doping concentration of Si in the layer is 1 x 10¹⁷/cm³-9×10¹⁸/cm³And the Al component is 40-80 wt%.

Preferably, the V-shaped defect array consists of a plurality of V-shaped defects distributed at intervals, and the opening size of the V-shaped defects is 90-200nm and the depth is 90-150 nm.

Preferably, the thickness of the MQW multi-quantum well light-emitting layer is 15-100 nm.

Preferably, the thickness of the P-type GaN layer is 50-300nm, and the doping concentration of Mg in the layer is more than 1 x 10¹⁸/cm³。

In order to solve another technical problem of the invention, the technical scheme is that the preparation method of the deep ultraviolet LED epitaxial structure comprises the following steps:

s1, the temperature of the reaction chamber is 1200-1400 ℃, and a high-temperature AlN layer is epitaxially grown on the substrate;

s2, growing an N-type AlGaN layer on the high-temperature AlN layer;

s3, etching the N-type AlGaN layer to form a V-shaped defect array;

s4, growing an MQW multi-quantum well light-emitting layer on the surface of the N-type AlGaN layer where the V-shaped defect array is located;

s5, growing a P-type GaN layer after the MQW multi-quantum well light-emitting layer finishes growing;

and S6, after the epitaxial growth is finished, reducing the temperature of the reaction chamber to between 450 and 800 ℃, annealing for 2-20min in a pure nitrogen atmosphere, and then reducing the temperature to room temperature to obtain the deep ultraviolet LED epitaxial structure.

Preferably, the Ga source in each layer is trimethyl gallium and triethyl gallium, the Al source is trimethyl aluminum, the N source is ammonia, silane is used as an N-type dopant, and magnesium chloride is used as a p-type dopant.

Compared with the prior art, the invention has the beneficial effects that:

1) in the existing deep ultraviolet LED epitaxial growth, an active region luminous layer is mainly of a planar structure. According to the invention, through the optimized V-shaped defect design before MQW, the light-emitting layer of the active region can be changed into a three-dimensional structure from a planar structure, and the original vertical direction has PN junctions and the horizontal direction also has PN junctions. Therefore, the carrier transport path and the recombination position can be effectively controlled and improved, the recombination efficiency is increased, and the luminous efficiency is improved.

2) The invention provides a deep ultraviolet LED epitaxial structure, which is characterized in that a high-temperature AlN layer grows on a substrate, an N-type AlGaN layer grows on the substrate, a V-shaped defect array is etched on the N-type AlGaN layer, and then the N-type AlGaN layer, an MQW multi-quantum well light-emitting layer and a P-type GaN layer grow in an epitaxial mode in sequence. The design of the V-shaped defects can release stress generated in the growth process on one hand; on the other hand, the growth method of the MQW multi-quantum well light-emitting layer is changed, namely the MQW multi-quantum well light-emitting layer is grown on the nonpolar surface of the V-shaped defect instead of the planar growth. The growth method can increase the light-emitting area of the UVC LED, improve the light-emitting brightness to obtain better light-emitting efficiency and release stress generated in the growth process.

3) The N-type AlGaN covering layer covering the V-shaped defect array in the deep ultraviolet LED epitaxial structure is used for transition or protection after epitaxial growth of a V-shaped defect pit, so that extension and expansion of harmful defects can be reduced.

Drawings

Fig. 1 is a schematic structural view of the deep ultraviolet LED epitaxial structure of the present invention without the N-type AlGaN cladding layer 6;

FIG. 2 is a schematic structural diagram of the deep ultraviolet LED epitaxial structure of the present invention including an N-type AlGaN cladding layer 6;

fig. 3 is a graph showing the change of the luminance of two deep ultraviolet LED epitaxial structures prepared in examples 2 and 3 with current.

The designations in the drawings have the following meanings:

1. a substrate; 2. a high temperature AlN layer; 3. an N-type AlGaN layer; 4. an MQW multiple quantum well light-emitting layer; 5. a P-type GaN layer; 6. an N-type AlGaN cladding layer;

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments, and all other embodiments obtained by a person of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the protection scope of the present invention.

Example 1

As shown in fig. 1, the deep ultraviolet LED epitaxy structure sequentially comprises a substrate 1, a high-temperature AlN layer 2, an N-type AlGaN layer 3, an MQW multiple quantum well light-emitting layer 4, and a P-type GaN layer 5 from bottom to top, wherein a V-shaped defect array is disposed on the N-type AlGaN layer 3, and the MQW multiple quantum well light-emitting layer 4 and the P-type GaN layer 5 continue epitaxial growth sequentially on a surface of the N-type AlGaN layer on which the V-shaped defect array is disposed.

Or, as shown in fig. 2, the deep ultraviolet LED epitaxy structure sequentially comprises, from bottom to top, a substrate 1, a high-temperature AlN layer 2, an N-type AlGaN layer 3, an N-type AlGaN cladding layer 6, an MQW multi-quantum well light-emitting layer 4, and a P-type GaN layer 5, wherein a V-shaped defect array is disposed on the N-type AlGaN layer 3, and the MQW multi-quantum well light-emitting layer 4 and the P-type GaN layer 5 are epitaxially grown in sequence on the surface of the V-shaped defect array on the N-type AlGaN layer.

The V-shaped defect array consists of a plurality of V-shaped defects distributed at intervals, the opening size of the V-shaped defects is 90-200nm, and the depth of the V-shaped defects is 90-150 nm; the substrate 1 is a sapphire flat sheet substrate or an NPSS substrate; the thickness of the high-temperature AlN layer 2 is 1.5-5 um; the thickness of the N-type AlGaN layer 3 is 0.5-3um, and the doping concentration of Si in the layer is 1 multiplied by 10¹⁷/cm³-9×10¹⁸/cm³The Al component is 40-80 wt%; the MQW multi-quantum well luminescent layer 4 has a thickness of 15-100nm and is composed of a quantum barrier layer Al_xGa_1-xN(45％<x<60%) and quantum well layer Al_yGa_1-yN(35％<y<50%) alternately, one quantum barrier layer and one quantum well layer are in one growth cycle, and the cycle number is 3-6; the thickness of the P-type GaN layer 5 is 50-300nm, and the doping concentration of Mg is more than 1 x 10¹⁸/cm³(ii) a The thickness of the N-type AlGaN covering layer 6 is 200-1000nm, and the Al component is 50-80 wt%.

Example 2

This example uses high purity hydrogen or nitrogen as carrier gas, trimethyl gallium (TMGa), triethyl gallium (TEGa), trimethyl aluminum (TMAl) and ammonia (NH)₃) Using Silane (SiH) as the source of Ga, Al and N, respectively₄) As an n-type dopant, magnesium dicocene (Cp)₂Mg) as a p-type dopant.

A preparation method of the deep ultraviolet LED epitaxial structure shown in FIG. 2 specifically comprises the following steps:

s1, growing a high-temperature AlN layer 2 on the sapphire flat substrate, wherein the thickness of the AlN layer is 2.5 um;

s2, growing an N-type AlGaN layer 3 on the high-temperature AlN layer 2, wherein the thickness of the N-type AlGaN layer is 2 mu m, and the doping concentration of Si is 7 multiplied by 10¹⁸/cm³The Al component is between 55 wt%;

s3, etching the N-type AlGaN layer 3 to form a V-shaped defect array, wherein the V-shaped defect array consists of a plurality of V-shaped defects, the size of an opening of each V-shaped defect is 100nm, and the depth of each V-shaped defect is 120 nm;

s4, growing an N-type AlGaN covering layer 6 on the surface of the N-type AlGaN layer 3 where the V-shaped defect array is located, wherein the thickness of the N-type AlGaN covering layer is 300nm, and the Al component is 55 wt%, so that the extension and expansion of harmful defects are reduced;

s5, growing a MQW multi-quantum well light-emitting layer 4 on the N-type AlGaN covering layer 6, wherein one quantum barrier layer and one quantum well layer form one growth cycle, 5 growth cycles are adopted, and the thickness of the whole MQW multi-quantum well light-emitting layer 4 is between 30 nm;

s6, after the growth of the MQW multi-quantum well light-emitting layer 4 is finished, growing a P-type GaN layer 5 with the thickness of 280nm and the Mg doping concentration of more than 1 x 10¹⁹/cm³。

And S7, after the epitaxial growth is finished, reducing the temperature of the reaction chamber to 450 ℃, annealing for 10min in a pure nitrogen atmosphere, and then reducing the temperature to room temperature to obtain the deep ultraviolet LED epitaxial structure.

Example 3

This example uses high purity hydrogen or nitrogen as carrier gas, trimethyl gallium (TMGa), triethyl gallium (TEGa), trimethyl aluminum (TMAl) and ammonia (NH)₃) Using Silane (SiH) as the source of Ga, Al and N, respectively₄) As an n-type dopant, magnesium dicocene (Cp)₂Mg) as a p-type dopant.

A preparation method of a deep ultraviolet LED epitaxial structure specifically comprises the following steps:

s1, growing a high-temperature AlN layer 2 on the sapphire flat substrate, wherein the thickness of the AlN layer is 2.5 um;

s2, growing an N-type AlGaN layer 3 on the high-temperature AlN layer 2, wherein the thickness of the N-type AlGaN layer is 2 mu m, and the doping concentration of Si is 7 multiplied by 10¹⁸/cm³The Al component is between 55 wt%;

s3, growing a MQW multi-quantum well light-emitting layer 4 on the N-type AlGaN layer 3, wherein one quantum barrier layer and one quantum well layer form a growth cycle, 5 growth periods are adopted, and the thickness of the whole MQW multi-quantum well light-emitting layer 4 is between 30 nm;

s6, after the growth of the MQW multi-quantum well light-emitting layer 4 is finished, growing a P-type GaN layer 5 with the thickness of 280nm and the Mg doping concentration of 1 multiplied by 10¹⁹/cm³。

And S7, after the epitaxial growth is finished, reducing the temperature of the reaction chamber to 450 ℃, annealing for 10min in a pure nitrogen atmosphere, and then reducing the temperature to room temperature to obtain the deep ultraviolet LED epitaxial structure.

The two deep ultraviolet LED epitaxial structures prepared in examples 2 and 3 were respectively tested for photoelectric performance to obtain a luminance magnification curve, as shown in fig. 3, the abscissa is current in milliampere (mA), the ordinate is the luminance ratio of the luminance of different currents to the luminance under the reference current, and the larger the ratio is, the better the luminance performance is. As can be seen from fig. 3, the deep ultraviolet LED epitaxial structure having V-type defects in example 2 has advantages in brightness compared to example 3, and the light emitting efficiency is improved.

It should be understood by those skilled in the art that the foregoing is only illustrative of several embodiments of the invention, and not of all embodiments. It should be noted that many variations and modifications are possible to those skilled in the art, and all variations and modifications that do not depart from the gist of the invention are intended to be within the scope of the invention as defined in the appended claims.