CN114203868A - Deep ultraviolet chip with n-type low-resistance ohmic contact structure and preparation method thereof - Google Patents
Deep ultraviolet chip with n-type low-resistance ohmic contact structure and preparation method thereof Download PDFInfo
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- 238000005530 etching Methods 0.000 claims abstract description 27
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- 229910052594 sapphire Inorganic materials 0.000 claims abstract description 9
- 239000010980 sapphire Substances 0.000 claims abstract description 9
- 239000000758 substrate Substances 0.000 claims abstract description 9
- 239000010410 layer Substances 0.000 claims description 296
- 238000000034 method Methods 0.000 claims description 12
- 238000000151 deposition Methods 0.000 claims description 11
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- 230000000052 comparative effect Effects 0.000 description 6
- 239000004065 semiconductor Substances 0.000 description 4
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- QSHDDOUJBYECFT-UHFFFAOYSA-N mercury Chemical compound [Hg] QSHDDOUJBYECFT-UHFFFAOYSA-N 0.000 description 3
- 229910052753 mercury Inorganic materials 0.000 description 3
- 150000004767 nitrides Chemical class 0.000 description 3
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Abstract
The invention discloses a deep ultraviolet chip with an n-type low-resistance ohmic contact structure and a preparation method thereof, wherein the deep ultraviolet chip comprises a sapphire substrate, an AlN intrinsic layer, an n-type AlGaN electron injection layer, an n-type AlGaN auxiliary expansion layer, an n-type AlGaN contact layer, a quantum well active layer, an electron blocking layer, a p-type AlGaN hole injection layer, a p-type GaN contact layer, a p electrode and an n electrode which are sequentially stacked; etching to the n-type AlGaN contact layer along one side of the p-type GaN contact layer, wherein the n-type AlGaN contact layer forms a step-shaped structure, and the n electrode is arranged at the etching region of the n-type AlGaN contact layer; along the direction from the n-type AlGaN electron injection layer to the n-type AlGaN contact layer, the doping concentration of the n-type AlGaN auxiliary expansion layer is increased linearly, and the percentage of Al component is decreased linearly. According to the invention, the n-type AlGaN auxiliary extension layer with gradually changed doping concentration and Al component percentage is introduced, so that the n-pole contact voltage of the deep ultraviolet LED chip is reduced, and the photoelectric conversion efficiency of the deep ultraviolet LED chip is remarkably improved.
Description
Technical Field
The invention relates to the field of semiconductor photoelectricity, in particular to a deep ultraviolet chip with an n-type low-resistance ohmic contact structure and a preparation method thereof.
Background
Group iii nitrides have achieved efficient solid-state light source devices such as blue-green light emitting diodes, lasers, and the like as an outstanding representative of wide bandgap semiconductor materials, with great success in applications such as flat panel displays, white light illumination, and the like. In the last decade, it has been desired to apply such efficient luminescent materials in the ultraviolet band to meet the increasing demand of ultraviolet light sources. At present, the traditional ultraviolet light source is mainly a mercury lamp, has the defects of large volume, high power consumption, high voltage, environmental pollution and the like, and is not beneficial to the application of the traditional ultraviolet light source in daily life and special environments. Therefore, it is highly desirable to develop a highly efficient semiconductor ultraviolet light source device to replace the conventional mercury lamp. The existing research shows that AlGaN in III group nitride is the best candidate material for preparing semiconductor ultraviolet light source devices, and the AlGaN-based ultraviolet LED has the advantages of no toxicity, environmental protection, small size, portability, low power consumption, low voltage, easy integration, long service life, adjustable wavelength and the like, is expected to make breakthrough progress and wide application in the coming years, and gradually replaces the traditional ultraviolet mercury lamp.
At present, AlxGa1-xThe forbidden bandwidth of the N material can be continuously adjusted in a range from 3.4eV (GaN) to 6.2eV (AlN) by changing the Al component, and light emission in a spectral range from 365nm to 200nm can be realized. The band edge emission wavelength of GaN is about 360nm, and is generally used as a division mark of the emission band of nitride ultraviolet light emitting diodes. The active region of UV-LEDs emitting light at wavelengths greater than 360nm uses a GaN/InGaN Quantum Well (QWs) structure similar to blue LEDs. The research related to the method has been started in the past 90 years, and the method is successfully commercialized, and the External Quantum Efficiency (EQE) is over 40 percent, and reaches the level comparable to that of a blue LED.
However, when a deep ultraviolet LED device is manufactured, the n-type AlGaN material has many limitations compared with the conventional manufacturing process of the n-GaN material, because the n-type AlGaN material with high Al content has a problem of difficult doping, and the manufacturing of the n-type ohmic contact electrode requires more severe process requirements; compared with GaN materials, AlGaN materials have large forbidden band width and poor crystal quality, so that the prepared n-type ohmic contact electrode has low resistance property and is difficult to have, and current is concentrated between an n-type electron injection layer and an n-type contact layer only by thinning an n-type contact layer; the low-resistance n-type ohmic contact electrode is difficult to prepare under the high Al content AlGaN material, so that the working voltage of the deep ultraviolet LED chip is difficult to reduce, and the photoelectric conversion efficiency of the ultraviolet epitaxial chip is restricted. Therefore, a new preparation method of the deep ultraviolet LED chip is needed to solve the above existing problems.
Disclosure of Invention
The invention aims to provide a deep ultraviolet chip with an n-type low-resistance ohmic contact structure and a preparation method thereof, which are used for solving the problem that in the prior art, current is concentrated between an n-type AlGaN electron injection layer and an n-type AlGaN contact layer, so that the efficiency of a deep ultraviolet LED is low.
In order to solve the above technical problem, a first solution provided by the present invention is: a deep ultraviolet chip with an n-type low-resistance ohmic contact structure comprises a sapphire substrate, an AlN intrinsic layer, an n-type AlGaN electron injection layer, an n-type AlGaN auxiliary expansion layer, an n-type AlGaN contact layer, a quantum well active layer, an electron blocking layer, a p-type AlGaN hole injection layer, a p-type GaN contact layer and a p electrode which are sequentially stacked, and further comprises an n electrode; etching to the n-type AlGaN contact layer along one side of the p-type GaN contact layer, wherein the n-type AlGaN contact layer forms a step-shaped structure, the n electrode is arranged at the etching region of the n-type AlGaN contact layer, and the thickness of the n-type AlGaN contact layer after etching is 0.1-0.9 times of the initial thickness of the n-type AlGaN contact layer; along the direction from the n-type AlGaN electron injection layer to the n-type AlGaN contact layer, the doping concentration of the n-type AlGaN auxiliary expansion layer is increased linearly, and the percentage of Al component is decreased linearly.
Preferably, the n-type AlGaN electron injection layer is of a Si-doped single-layer AlGaN structure, the Al component percentage of the n-type AlGaN electron injection layer is 70-100%, and the thickness of the n-type AlGaN electron injection layer is 500-4000 nm.
Preferably, the n-type AlGaN contact layer is of a Si-doped single-layer AlGaN structure, the Al component percentage of the n-type AlGaN contact layer is 40-80%, and the thickness of the n-type AlGaN contact layer is 10-1000 nm.
Preferably, the percentage of the Al component of the n-type AlGaN electron injection layer and the n-type AlGaN contact layer satisfies the following conditions: x is less than y, x is the Al component percentage of the n-type AlGaN contact layer, and y is the Al component percentage of the n-type AlGaN electron injection layer.
Preferably, the Si doping concentrations of the n-type AlGaN electron injection layer and the n-type AlGaN contact layer satisfy: and a is the Si doping concentration of the n-type AlGaN contact layer, and b is the Si doping concentration of the n-type AlGaN electron injection layer.
Preferably, after etching, the distance between the etched surface of the n-type AlGaN contact layer and the n-type AlGaN electron injection layer is 50-3500 nm, and the distance between the etched surface of the n-type AlGaN contact layer and the quantum well active layer is 50-500 nm.
In order to solve the above technical problem, a second solution provided by the present invention is: a method for manufacturing a deep ultraviolet chip having an n-type low-resistance ohmic contact structure as in the first solution, comprising the steps of:
(1) an AlN intrinsic layer was grown on the sapphire substrate.
(2) And growing an n-type AlGaN electron injection layer on the AlN intrinsic layer.
(3) And growing an n-type AlGaN auxiliary extension layer on the n-type AlGaN electron injection layer.
(4) And growing an n-type AlGaN contact layer on the n-type AlGaN auxiliary extension layer.
(5) And sequentially growing a quantum well active layer, an electron blocking layer, a p-type AlGaN hole injection layer and a p-type GaN contact layer on the n-type AlGaN contact layer.
(6) Etching and forming a step-shaped structure: and etching to the n-type AlGaN contact layer along one side of the p-type GaN contact layer to form a stepped structure, wherein the thickness of the n-type AlGaN contact layer after etching is-times of the initial thickness of the n-type AlGaN contact layer.
(7) Depositing a p electrode and an n electrode: and depositing a p electrode on the p-type GaN contact layer, and depositing an n electrode on the etched n-type AlGaN contact layer to obtain the deep ultraviolet chip with the n-type low-resistance ohmic contact structure.
Preferably, the step (2) and the step (4) satisfy that T1< T2, wherein T1 is the growth temperature of the n-type AlGaN contact layer, and T2 is the growth temperature of the n-type AlGaN electron injection layer; in the step (3), the n-type AlGaN auxiliary expansion layer grows in a linearly decreasing temperature mode, and the growth temperature of the n-type AlGaN auxiliary expansion layer is gradually changed from T2 to T1.
Preferably, in the step (2) and the step (4), x is less than y, wherein x is the percentage of the Al component of the n-type AlGaN contact layer, y is the percentage of the Al component of the n-type AlGaN electron injection layer, y is more than or equal to 70% and less than or equal to 100%, and x is more than or equal to 40% and less than or equal to 80%; in the step (3), the n-type AlGaN auxiliary expansion layer grows in a way that the Al component percentage is linearly decreased, and the Al component percentage of the n-type AlGaN auxiliary expansion layer is gradually changed from y to x.
Preferably, step (2) and step (4) satisfy the condition that a>b, where a is the Si doping concentration of the n-type AlGaN contact layer, and b is the Si doping concentration of the n-type AlGaN electron injection layer, 1019≤a≤1021cm-3(ii) a In the step (3), the n-type AlGaN auxiliary expansion layer grows in a way that the Si doping concentration increases progressively linearly, and the Si doping concentration of the n-type AlGaN auxiliary expansion layer is gradually changed from b to a.
The invention has the beneficial effects that: the deep ultraviolet LED chip is characterized in that an n-type AlGaN auxiliary expansion layer with gradually changed doping concentration and Al component percentage is introduced between an n-type AlGaN electron injection layer and an n-type AlGaN contact layer, so that the n-pole contact voltage of the deep ultraviolet LED chip is reduced, and the photoelectric conversion efficiency of the deep ultraviolet LED chip is remarkably improved.
Drawings
FIG. 1 is a schematic structural diagram of an embodiment of a deep ultraviolet chip having an n-type low resistance ohmic contact structure according to the present invention;
fig. 2 is a graph comparing the light output power of samples of the deep ultraviolet LEDs of example 1 and comparative example 1 in accordance with the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.
Referring to fig. 1, fig. 1 is a schematic structural diagram of an embodiment of a deep ultraviolet chip having an n-type low-resistance ohmic contact structure according to the present invention. The deep ultraviolet chip with the n-type low-resistance ohmic contact structure comprises a sapphire substrate 1, an AlN intrinsic layer 2, an n-type AlGaN electron injection layer 3, an n-type AlGaN auxiliary expansion layer 4, an n-type AlGaN contact layer 5, a quantum well active layer 6, an electron blocking layer 7, a p-type AlGaN hole injection layer 8, a p-type GaN contact layer 9 and a p electrode 10 which are sequentially stacked, and further comprises an n electrode 11; etching to the n-type AlGaN contact layer 5 along one side of the p-type GaN contact layer 9, wherein the n-type AlGaN contact layer 5 forms a step-shaped structure, and the n electrode 11 is arranged at the etching region of the n-type AlGaN contact layer 5; along the direction from the n-type AlGaN electron injection layer 3 to the n-type AlGaN contact layer 5, the doping concentration of the n-type AlGaN auxiliary expansion layer 4 is increased in a linear mode, the percentage of Al components is decreased in a linear mode, and the n-type AlGaN auxiliary expansion layer with the gradually changed doping concentration and Al component percentage is introduced to reduce the n-pole contact voltage of the deep ultraviolet LED chip.
In the embodiment, the n-type AlGaN electron injection layer 3 is a Si-doped single-layer AlGaN structure, the Al component percentage of the n-type AlGaN electron injection layer is 70-100%, and the thickness of the n-type AlGaN electron injection layer is 500-4000 nm; the n-type AlGaN contact layer 5 is of a Si-doped single-layer AlGaN structure, the Al component percentage of the n-type AlGaN contact layer is 40-80%, and the thickness of the n-type AlGaN contact layer is 10-1000 nm. The Al component percentages of the two film layers of the n-type AlGaN electron injection layer 3 and the n-type AlGaN contact layer 5 meet the following requirements: x is less than y, x is the Al component percentage of the n-type AlGaN contact layer, and y is the Al component percentage of the n-type AlGaN electron injection layer; the Si doping concentrations of the n-type AlGaN electron injection layer and the n-type AlGaN contact layer meet the following conditions: and a is the Si doping concentration of the n-type AlGaN contact layer, and b is the Si doping concentration of the n-type AlGaN electron injection layer.
Specifically, the thickness of the etched n-type AlGaN contact layer is 0.1-0.9 times of the initial thickness of the n-type AlGaN contact layer, and preferably, the thickness of the etched n-type AlGaN contact layer is half of the initial thickness of the n-type AlGaN contact layer; preferably, after etching, the distance between the etched surface of the n-type AlGaN contact layer and the n-type AlGaN electron injection layer is 50-3500 nm, and the distance between the etched surface of the n-type AlGaN contact layer and the quantum well active layer is 50-500 nm.
In the embodiment, the deep ultraviolet chip with the n-type low-resistance ohmic contact structure is prepared by adopting an MOCVD method, Si acting n-type dopant is adopted in the n-type AlGaN electron injection layer 3, the n-type AlGaN auxiliary expansion layer 4 and the n-type AlGaN contact layer 5, and Mg is adopted as p-type dopant in the p-type AlGaN hole injection layer 8 and the p-type GaN contact layer 9. In addition, an n electrode 11 is disposed on the etched n-type AlGaN contact layer 5 and a p electrode 10 is disposed on the p-type GaN contact layer 9 by a conventional method, which is not described herein again.
For the second solution proposed by the invention, the preparation method of the deep ultraviolet chip with the n-type low-resistance ohmic contact structure comprises the following steps:
(1) an AlN intrinsic layer was grown on the sapphire substrate. In the embodiment, a low-temperature buffer layer in an AlN intrinsic layer grows on a sapphire substrate at the temperature of 400-800 ℃, and the thickness of the low-temperature buffer layer is 10-50 nm; and heating to 1200-1400 ℃, and growing an AlN intrinsic layer on the low-temperature buffer layer in the AlN intrinsic layer, wherein the total thickness of the AlN intrinsic layer is 500-4000 nm.
(2) And growing an n-type AlGaN electron injection layer on the AlN intrinsic layer. In the embodiment, the temperature is reduced to 800-1200 ℃, an n-type AlGaN electron injection layer is grown on the AlN intrinsic layer, wherein the Al component percentage is 70-100%, the thickness is 500-4000 nm, and Si is used as an n-type dopant.
(3) And growing an n-type AlGaN auxiliary extension layer on the n-type AlGaN electron injection layer. In this embodiment, the n-type AlGaN auxiliary extension layer has a thickness of 1 to 2000nm, and Si is used as the n-type dopant.
(4) And growing an n-type AlGaN contact layer on the n-type AlGaN auxiliary extension layer. In the embodiment, an n-type AlGaN contact layer is grown on an n-type AlGaN auxiliary expansion layer, wherein the Al component percentage is 40-80%, the initial thickness is 10-1000 nm, and Si is used as an n-type dopant; the preferred doping concentration is 1019～1021cm-3Experiments show that the doping concentration in the n-type AlGaN contact layer cannot be lower than a limited doping concentration, a good activation effect cannot be obtained easily after the doping concentration is lower than the limited doping concentration, and when the doping concentration is too high, a doping element permeates and transfers to an adjacent film layer, so that the n-type AlGaN contact layer is preferably maintained in the limited range.
Specifically, the n-type AlGaN electron injection layer, the n-type AlGaN auxiliary expansion layer, and the n-type AlGaN contact layer prepared in steps (2) to (4) need to satisfy the following three conditions during the preparation process:
a. regarding the growth temperature, the step (2) and the step (4) satisfy that T1< T2, where T1 is the growth temperature of the n-type AlGaN contact layer, and T2 is the growth temperature of the n-type AlGaN electron injection layer; in the step (3), the n-type AlGaN auxiliary expansion layer grows in a linearly decreasing temperature mode, and the growth temperature of the n-type AlGaN auxiliary expansion layer is gradually changed from T2 to T1.
b. Regarding the percentage of the Al component, the requirements in the step (2) and the step (4) are that x is less than y, wherein x is the percentage of the Al component of the n-type AlGaN contact layer, y is the percentage of the Al component of the n-type AlGaN electron injection layer, y is more than or equal to 70% and less than or equal to 100%, and x is more than or equal to 40% and less than or equal to 80%; in the step (3), the n-type AlGaN auxiliary expansion layer grows in a way that the Al component percentage is linearly decreased, and the Al component percentage of the n-type AlGaN auxiliary expansion layer is gradually changed from y to x.
c. Regarding the doping concentration, the step (2) and the step (4) satisfy that a>b, wherein a is the Si doping concentration of the n-type AlGaN contact layer and b is the Si doping concentration of the n-type AlGaN electron injection layer, preferably 1019≤a≤1021cm-3(ii) a In the step (3), the n-type AlGaN auxiliary expansion layer grows in a way that the Si doping concentration increases progressively linearly, and the Si doping concentration of the n-type AlGaN auxiliary expansion layer is gradually changed from b to a.
(5) And sequentially growing a quantum well active layer, an electron blocking layer, a p-type AlGaN hole injection layer and a p-type GaN contact layer on the n-type AlGaN contact layer.
In this embodiment, the specific steps of growing the quantum well active layer with gradually changed components are as follows: under the condition of 700-1100 ℃, a quantum well active layer grows on the n-type AlGaN contact layer, the thickness of a potential barrier in the quantum well active layer is 5-30 nm, the percentage of the component of potential barrier Al is 20-100%, the thickness of a potential well is 0.1-5 nm, and the percentage of the component of potential well Al is 0.1-80%.
In this embodiment, the specific steps of growing the electron blocking layer are as follows: and growing an electron barrier layer on the quantum well active layer at 700-1100 ℃, wherein the thickness of the electron barrier layer is 5-30 nm, and the percentage of the Al component is 30-100%.
In this embodiment, the specific steps of growing the p-type AlGaN hole injection layer are as follows: growing a p-type AlGaN hole injection layer on the electron blocking layer at 700-1100 ℃, wherein the Al component percentage is 0.1-100%, the thickness is 1-50 nm, and Mg is used as a p-type dopant.
In this embodiment, the specific steps of growing the p-type GaN contact layer are as follows: growing a p-type GaN contact layer on the p-type AlGaN hole injection layer at the temperature of 400-900 ℃, wherein the thickness of the p-type GaN contact layer is 1-400 nm, and Mg is used as a p-type dopant.
(6) And etching and forming a step-shaped structure. In this embodiment, the MESA etching system is used to etch the p-type GaN contact layer to the n-type AlGaN contact layer along one side thereof, and a stepped structure is formed, and the thickness of the n-type AlGaN contact layer after etching is equal to-times of the initial thickness of the n-type AlGaN contact layer.
(7) Depositing a p electrode and an n electrode: and depositing a p electrode on the p-type GaN contact layer, and depositing an n electrode on the etched n-type AlGaN contact layer to obtain the deep ultraviolet chip with the n-type low-resistance ohmic contact structure.
Since the method for manufacturing a deep ultraviolet chip having an n-type low-resistance ohmic contact structure in the second solution is used to manufacture the deep ultraviolet chip having an n-type low-resistance ohmic contact structure in the first solution, the structure and function of the deep ultraviolet chip having an n-type low-resistance ohmic contact structure in the two solutions should be consistent.
Further, the design principle of the deep ultraviolet chip with the n-type low-resistance ohmic contact structure is explained as follows: after the n-type AlGaN contact layer is etched, the distance between the surface of the etched part and the n-type AlGaN electron injection layer is too close, and a current concentration effect is easily formed at the edge of an n electrode, so that the current concentration problem is well solved by strictly limiting the etching depth of the n-type AlGaN contact layer, forming a low-resistance n-type ohmic contact electrode structure and simultaneously introducing an n-type AlGaN auxiliary expansion layer, so that the current is easier to transversely expand to a quantum well active region; the proportion of Al components in the n-type AlGaN electron injection layer is higher than that in the n-type AlGaN contact layer, and the stress can be well released by the n-type AlGaN auxiliary expansion layer in a mode of gradually changing the proportion of the Al components; the n-type AlGaN auxiliary expansion layer adopts a gradual doping mode, the doping concentration is higher at the position closer to the n-type AlGaN contact layer, and the design mode can ensure that the current can be longitudinally diffused to a deeper distance in the n-type AlGaN auxiliary expansion layer.
The performance and effect of the deep ultraviolet chip with the n-type low-resistance ohmic contact structure are characterized through specific embodiments.
Example 1
In this embodiment, the step of preparing the deep ultraviolet chip having the n-type low-resistance ohmic contact structure is as follows:
1) growing a low-temperature buffer layer in the AlN intrinsic layer on the sapphire substrate at 700 ℃, wherein the thickness of the low-temperature buffer layer is 20 nm; and raising the temperature to 1200 ℃, and growing an AlN intrinsic layer on the low-temperature buffer layer in the AlN intrinsic layer, wherein the total thickness of the AlN intrinsic layer is 800 nm.
2) Growing an n-type AlGaN electron injection layer on the AlN intrinsic layer at 1000 ℃, wherein the thickness of the n-type AlGaN electron injection layer is 1000nm, the Al component percentage is 80 percent, and the Si doping concentration is 1018cm-3。
3) Growing an n-type AlGaN auxiliary expansion layer on the n-type AlGaN electron injection layer, wherein the thickness is 1000nm, the growth temperature is linearly decreased from 1000 ℃ to 900 ℃, the percentage of Al components is linearly decreased from 80% to 60%, and the doping concentration of Si is linearly decreased from 10%18cm-3Linear increment to 1020cm-3。
4) Growing an n-type AlGaN contact layer on the n-type AlGaN auxiliary expansion layer at 900 ℃, wherein the thickness of the n-type AlGaN contact layer is 1000nm, the Al component percentage is 60 percent, and the Si doping concentration is 1020cm-3。
5) Growing a quantum well active layer on the n-type AlGaN contact layer at 850 ℃, wherein the AlGaN potential well layer is Al0.4Ga0.6N, the thickness of each potential well layer is 5 nm; AlGaN potentialThe barrier layer is Al0.5Ga0.5And N, the thickness of each barrier layer is 5nm, and 5 periods of alternate growth are completed to obtain the quantum well active layer.
6) And (3) growing an electron barrier layer on the quantum well active layer at the temperature of 750 ℃, wherein the thickness of the electron barrier layer is 10nm, and the percentage of the Al component is 50%.
7) Growing a p-type AlGaN hole injection layer on the electron blocking layer at 800 ℃, wherein the Al component percentage is 20%, the thickness is 20nm, and Mg is used as a p-type dopant.
8) And growing a p-type GaN contact layer on the p-type AlGaN hole injection layer at the temperature of 800 ℃, wherein the thickness of the p-type GaN contact layer is 10nm, and Mg is used as a p-type dopant.
9) And etching to the n-type AlGaN contact layer along one side of the p-type GaN contact layer by using an MESA etching system, wherein the thickness of the n-type AlGaN contact layer after etching is half of the initial thickness of the n-type AlGaN contact layer.
10) And depositing a p electrode on the p-type GaN contact layer, and depositing an n electrode on the etched n-type AlGaN contact layer to obtain a deep ultraviolet chip sample with an n-type low-resistance ohmic contact structure.
Comparative example 1
This comparative example is based on the preparation procedure of example 1, except that no n-type AlGaN auxiliary extension layer is grown, and no etching thinning is performed on the n-type AlGaN contact layer, and other preparation parameters are consistent with those of example 1.
The samples of example 1 and comparative example 1 were compared and the light output power test was performed, and the results are shown in fig. 2, respectively, the contact voltage of the deep ultraviolet LED chip prepared in example 1 was significantly lower than that of comparative example 1, taking the current of 40mA as an example, the contact voltage of the deep ultraviolet LED chip of comparative example 1 was 5.72V, and the contact voltage of the deep ultraviolet LED chip of example 1 was 4.99V. According to the electro-optic conversion efficiency formula: the photoelectric conversion efficiency is output optical power/input electric power is output optical power/(working voltage × working current), and when the working voltage of the deep ultraviolet LED chip in embodiment 1 is significantly decreased, the photoelectric conversion efficiency is significantly improved, thereby proving that the method of the present invention can effectively improve the photoelectric conversion efficiency of the deep ultraviolet LED chip.
The deep ultraviolet LED chip is characterized in that an n-type AlGaN auxiliary expansion layer with gradually changed doping concentration and Al component percentage is introduced between an n-type AlGaN electron injection layer and an n-type AlGaN contact layer, so that the n-pole contact voltage of the deep ultraviolet LED chip is reduced, and the photoelectric conversion efficiency of the deep ultraviolet LED chip is remarkably improved.
The above-mentioned embodiments only express the embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.
Claims (10)
1. The deep ultraviolet chip with the n-type low-resistance ohmic contact structure is characterized by comprising a sapphire substrate, an AlN intrinsic layer, an n-type AlGaN electron injection layer, an n-type AlGaN auxiliary expansion layer, an n-type AlGaN contact layer, a quantum well active layer, an electron blocking layer, a p-type AlGaN hole injection layer, a p-type GaN contact layer and a p electrode which are sequentially stacked, and the deep ultraviolet chip further comprises an n electrode;
etching to the n-type AlGaN contact layer along one side of the p-type GaN contact layer, wherein the n-type AlGaN contact layer forms a step-shaped structure, the n electrode is arranged at an etching area of the n-type AlGaN contact layer, and the thickness of the n-type AlGaN contact layer after etching is 0.1-0.9 times of the initial thickness of the n-type AlGaN contact layer;
along the direction from the n-type AlGaN electron injection layer to the n-type AlGaN contact layer, the doping concentration of the n-type AlGaN auxiliary expansion layer increases linearly, and the percentage of Al component decreases linearly.
2. The deep ultraviolet chip with the n-type low-resistance ohmic contact structure according to claim 1, wherein the n-type AlGaN electron injection layer is of a Si-doped single-layer AlGaN structure, the Al component percentage of the n-type AlGaN electron injection layer is 70-100%, and the thickness of the n-type AlGaN electron injection layer is 500-4000 nm.
3. The deep ultraviolet chip with the n-type low-resistance ohmic contact structure according to claim 1, wherein the n-type AlGaN contact layer is of a Si-doped single-layer AlGaN structure, has an Al component percentage of 40-80% and a thickness of 10-1000 nm.
4. The deep ultraviolet chip with the n-type low-resistance ohmic contact structure according to claim 1, wherein the Al composition percentages of the n-type AlGaN electron injection layer and the n-type AlGaN contact layer satisfy: x is less than y, x is the Al component percentage of the n-type AlGaN contact layer, and y is the Al component percentage of the n-type AlGaN electron injection layer.
5. The deep ultraviolet chip with the n-type low-resistance ohmic contact structure according to claim 1, wherein the Si doping concentrations of the n-type AlGaN electron injection layer and the n-type AlGaN contact layer satisfy the following conditions: and a is the Si doping concentration of the n-type AlGaN contact layer, and b is the Si doping concentration of the n-type AlGaN electron injection layer.
6. The deep ultraviolet chip with the n-type low-resistance ohmic contact structure according to claim 1, wherein after etching, a distance between an etched surface of the n-type AlGaN contact layer and the n-type AlGaN electron injection layer is 50 to 3500nm, and a distance between an etched surface of the n-type AlGaN contact layer and the quantum well active layer is 50 to 500 nm.
7. A method for preparing the deep ultraviolet chip with the n-type low-resistance ohmic contact structure as claimed in any one of claims 1 to 6, comprising the following steps:
(1) growing an AlN intrinsic layer on the sapphire substrate;
(2) growing an n-type AlGaN electron injection layer on the AlN intrinsic layer;
(3) growing an n-type AlGaN auxiliary expansion layer on the n-type AlGaN electron injection layer;
(4) growing an n-type AlGaN contact layer on the n-type AlGaN auxiliary expansion layer;
(5) sequentially growing a quantum well active layer, an electron blocking layer, a p-type AlGaN hole injection layer and a p-type GaN contact layer on the n-type AlGaN contact layer;
(6) etching and forming a step-shaped structure: etching to the n-type AlGaN contact layer along one side of the p-type GaN contact layer to form a stepped structure, wherein the thickness of the n-type AlGaN contact layer after etching is-times of the initial thickness of the n-type AlGaN contact layer;
(7) depositing a p electrode and an n electrode: and depositing a p electrode on the p-type GaN contact layer, and depositing an n electrode on the etched n-type AlGaN contact layer to obtain the deep ultraviolet chip with the n-type low-resistance ohmic contact structure.
8. The method for manufacturing a deep ultraviolet chip with an n-type low-resistance ohmic contact structure according to claim 7, wherein the steps (2) and (4) satisfy that T1< T2, wherein T1 is the growth temperature of the n-type AlGaN contact layer, and T2 is the growth temperature of the n-type AlGaN electron injection layer;
in the step (3), the n-type AlGaN auxiliary extension layer grows in a linearly decreasing temperature manner, and the growth temperature of the n-type AlGaN auxiliary extension layer is gradually changed from T2 to T1.
9. The method for preparing the deep ultraviolet chip with the n-type low-resistance ohmic contact structure as claimed in claim 7, wherein x is less than y in the step (2) and the step (4), wherein x is the percentage of the Al component of the n-type AlGaN contact layer, y is the percentage of the Al component of the n-type AlGaN electron injection layer, y is more than or equal to 70% and less than or equal to 100%, and x is more than or equal to 40% and less than or equal to 80%;
in the step (3), the n-type AlGaN auxiliary expansion layer grows in a manner that the percentage of the Al component is linearly decreased, and the percentage of the Al component of the n-type AlGaN auxiliary expansion layer is gradually changed from y to x.
10. The method for preparing a deep ultraviolet chip with an n-type low-resistance ohmic contact structure according to claim 7Characterized in that the steps (2) and (4) are satisfied in that a>b, where a is the Si doping concentration of the n-type AlGaN contact layer, and b is the Si doping concentration of the n-type AlGaN electron injection layer, 1019≤a≤1021cm-3；
In the step (3), the n-type AlGaN auxiliary extension layer grows in a manner that the Si doping concentration increases linearly, and the Si doping concentration of the n-type AlGaN auxiliary extension layer is gradually changed from b to a.
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| CN115832136A (en) * | 2023-02-22 | 2023-03-21 | 江西兆驰半导体有限公司 | AlGaN-based ultraviolet light-emitting diode and preparation method thereof |
| CN115842079A (en) * | 2022-11-30 | 2023-03-24 | 江西兆驰半导体有限公司 | AlGaN-based ultraviolet LED epitaxial structure, LED and preparation method thereof |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN115842079A (en) * | 2022-11-30 | 2023-03-24 | 江西兆驰半导体有限公司 | AlGaN-based ultraviolet LED epitaxial structure, LED and preparation method thereof |
| CN115842079B (en) * | 2022-11-30 | 2024-02-02 | 江西兆驰半导体有限公司 | AlGaN-based ultraviolet LED epitaxial structure, LED and preparation method thereof |
| CN115832136A (en) * | 2023-02-22 | 2023-03-21 | 江西兆驰半导体有限公司 | AlGaN-based ultraviolet light-emitting diode and preparation method thereof |
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