CN115799417B - Ultraviolet light-emitting diode and preparation method thereof - Google Patents
Ultraviolet light-emitting diode and preparation method thereof Download PDFInfo
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Abstract
The invention discloses an ultraviolet light-emitting diode and a preparation method thereof, and relates to the technical field of semiconductors. The invention aims to improve the doping efficiency and the carrier concentration of the N-type semiconductor layer so as to improve the luminous efficiency of the ultraviolet light-emitting diode.
Description
Technical Field
The invention relates to the technical field of semiconductor devices, in particular to an ultraviolet light-emitting diode and a preparation method thereof.
Background
Ultraviolet light emitting diodes based on group III nitride semiconductor materials have a series of excellent characteristics of small size, portability, easy integration, no mercury, environmental protection, low power consumption, rapid switching, etc., and the emission wavelength covers the wavelength band of long-wave ultraviolet (UVA, 315-400 nm), medium-wave ultraviolet (UVB, 280-315 nm) to short-wave ultraviolet (UVC, 210-280 nm), and have wide application requirements in the fields of sterilization, medical care, industrial catalysis, photocuring, non-line-of-sight communication, biochemical detection, etc., and are regarded as ideal choices for replacing traditional ultraviolet light sources such as mercury lamps.
However, n-type and p-type materials of high quality, high carrier concentration uv leds are difficult to obtain. This is because the n-type and p-type doping efficiency of AlGaN materials with high Al composition is much lower than GaN materials, and as the Al composition increases, the forbidden bandwidth of AlGaN materials increases, the donor and acceptor energy levels gradually deepen, the activation energy continues to increase, and the dopant activation efficiency decreases. Furthermore, the free carrier concentration and conductivity in AlGaN materials are low, the subsequent ohmic contact preparation becomes difficult, the turn-on voltage of the ultraviolet LED thus becomes larger, and WPE decreases, so that the light emitting efficiency is insufficient.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide an ultraviolet light-emitting diode and a preparation method thereof, so as to solve the technical problem of insufficient luminous efficiency of the ultraviolet light-emitting diode in the prior art.
A first aspect of the present invention provides an ultraviolet light emitting diode, including a substrate, a buffer layer, an N-type semiconductor layer, an active region light emitting layer, an electron blocking layer, a P-type semiconductor layer, an ohmic contact layer, an N-electrode and a P-electrode, which are sequentially stacked from bottom to top:
the N-type semiconductor layer comprises a porous AlGaN layer, a first AlGaN gradient layer and a second AlGaN gradient layer which are sequentially laminated on the buffer layer, a stress release hole is formed in the porous AlGaN layer, the first AlGaN gradient layer is made of graded AlGaN materials with gradually decreasing Al components and gradually increasing Si doping concentrations, the stress release hole of the porous AlGaN layer is filled, the second AlGaN gradient layer is made of graded AlGaN materials with gradually increasing Al components and gradually decreasing Si doping concentrations, and the N electrode is laminated on one side surface of the first AlGaN gradient layer, which is far away from the porous AlGaN layer.
According to an aspect of the foregoing technical solution, the stress relief hole is disposed through the porous AlGaN layer.
According to an aspect of the above technical solution, the stress release hole has a V-shaped structure, and the aperture decreases in sequence along the direction from the first AlGaN graded layer to the buffer layer.
According to an aspect of the above technical solution, the stress release holes have a plurality of stress release holes, and each stress release hole has a uniform size, and the stress release holes are uniformly arranged in the porous AlGaN layer.
According to an aspect of the foregoing aspect, the stress relief holes have a density of 1×10 in the porous AlGaN layer 7 -1×10 10 /cm 2 。
According to an aspect of the above technical solution, the porous AlGaN layer is low Si element doped Al x Ga (1-x) N single-layer or multi-layer structure, wherein x is more than or equal to 0 and less than or equal to 1, the thickness of the porous AlGaN layer is 0.01 mu m-5 mu m, and the Si concentration is 1 multiplied by 10 8 /cm³-1×10 18 /cm³。
According to an aspect of the above technical solution, the first AlGaN graded layer is graded Al with decreasing Al composition and increasing Si doping concentration x Ga (1-x) N material, wherein Al component x decreases from x1 to x2 from bottom to top, si doping concentration c increases from c1 to c2, x2 is more than or equal to 0.4 and less than or equal to x1 and less than or equal to 1, thickness is 1 μm-3 μm, si doping concentration c1 is 2×10 17 A/cm. Delta. And a Si doping concentration c2 of 5X 10 18 /cm³。
According to an aspect of the above technical solution, the second AlGaN graded layer is graded Al with increasing Al composition and decreasing Si doping concentration x Ga (1-x) N material, wherein the Al component x increases from x3 to x4 from bottom to top, the Si doping concentration c decreases from c3 to c4, x3 is more than or equal to 0.4 and less than or equal to x4 and less than or equal to 1, the thickness is 1 mu m-3 mu m, and the Si doping concentration c3 is 5 multiplied by 10 18 The density c4 of Si doping is 2X 10 17 /cm³。
A second aspect of the present invention provides a method for preparing an ultraviolet light emitting diode, where the method is used for preparing the ultraviolet light emitting diode according to the above technical solution, and the method includes:
providing a substrate and growing a buffer layer on the substrate;
growing a porous AlGaN layer with stress release holes on the buffer layer based on preset growth conditions;
sequentially growing a first AlGaN gradient layer and a second AlGaN gradient layer on the porous AlGaN layer, and controlling the first AlGaN gradient layer to fill the stress release hole to obtain an N-type semiconductor layer, wherein the first AlGaN gradient layer is a gradient AlGaN material with gradually decreasing Al component and gradually increasing Si doping concentration, and the second AlGaN gradient layer is a gradient AlGaN material with gradually increasing Al component and gradually decreasing Si doping concentration;
sequentially growing an active region light-emitting layer, an electron blocking layer, a P-type semiconductor layer and an ohmic contact layer on the N-type semiconductor layer;
etching the ohmic contact layer until the surface of the first AlGaN graded layer is exposed;
and growing a P electrode on the surface of the unetched area of the ohmic contact layer, and growing an N electrode on the surface of the exposed first AlGaN graded layer to obtain the ultraviolet light emitting diode.
According to an aspect of the above technical solution, in the step of growing the porous AlGaN layer with the stress release hole on the buffer layer based on the preset growth condition, the stress release hole penetrates through the porous AlGaN layer and is in a V-shaped structure, and the aperture sequentially decreases along the direction from the first AlGaN graded layer to the buffer layer.
Compared with the prior art, the ultraviolet light-emitting diode and the preparation method thereof have the beneficial effects that:
through setting up into porous AlGaN layer, first AlGaN graded layer and second AlGaN graded layer with N type semiconductor layer, be equipped with a plurality of stress relief holes on the porous AlGaN layer to can release the stress of N type semiconductor layer, promote epitaxial layer quality, and be favorable to the Si atom to mix N type semiconductor after epitaxial layer's stress obtains releasing, promote N type semiconductor layer's doping efficiency and carrier concentration, simultaneously, locate the surface of first AlGaN graded layer with the N electrode, reduced the ohmic contact resistance of N electrode and N type semiconductor layer, in a word, can effectively promote ultraviolet light emitting diode's luminous efficacy.
Drawings
The foregoing and/or additional aspects and advantages of the invention will become apparent and may be better understood from the following description of embodiments taken in conjunction with the accompanying drawings in which:
FIG. 1 is a schematic view of an ultraviolet LED according to a first embodiment of the present invention;
FIG. 2 is a flow chart of a method for manufacturing an ultraviolet LED according to a second embodiment of the present invention;
description of the drawings:
the semiconductor device comprises a substrate 100, a buffer layer 200, an N-type semiconductor layer 300, a porous AlGaN layer 301, a stress release hole 3010, a first AlGaN graded layer 302, a second AlGaN graded layer 303, an active region light emitting layer 400, an electron blocking layer 500, a P-type semiconductor layer 600, an ohmic contact layer 700, an N electrode 800 and a P electrode 900.
Detailed Description
In order to make the objects, features and advantages of the present invention more comprehensible, embodiments accompanied with figures are described in detail below. Several embodiments of the invention are presented in the figures. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.
It will be understood that when an element is referred to as being "mounted" on another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present. The terms "vertical," "horizontal," "left," "right," and the like are used herein for illustrative purposes only.
Unless defined otherwise, 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 invention belongs. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and/or" as used herein includes any and all combinations of one or more of the associated listed items.
Example 1
Referring to fig. 1, a first embodiment of the present invention provides an ultraviolet light emitting diode, which includes a substrate 100, a buffer layer 200, an N-type semiconductor layer 300, an active region light emitting layer 400, an electron blocking layer 500, a P-type semiconductor layer 600, an ohmic contact layer 700, an N-electrode 800 and a P-electrode 900, which are sequentially stacked from bottom to top:
in this embodiment, the N-type semiconductor layer 300 includes a porous AlGaN layer 301, a first AlGaN graded layer 302 and a second AlGaN graded layer 303, specifically, the Al composition and doped Si element in the first AlGaN graded layer 302 and the second AlGaN graded layer 303 are graded along with their thickness or growth period, and are therefore called graded layers.
Wherein, a plurality of stress release holes 3010 are arranged on the side, facing the buffer layer 200, of the surface of the porous AlGaN layer 301 away from the buffer layer 200, and the plurality of stress release holes 3010 are uniform in size and are uniformly distributed in the porous AlGaN layer 301. In some possible embodiments, the density of stress relief holes 3010 is 1×10 7 /cm 2 -1×10 10 /cm 2 . In a preferred embodiment, the stress relief holes 3010 have a density of 5×10 8 /cm 2 That is, 5X 10 is provided per 1 square centimeter 8 The stress relief holes 3010 are uniformly sized and arranged in the 1 cm square.
In a preferred embodiment, the hole pattern of the stress release hole 3010 is a polygonal cone, and the cross section of the hole pattern is V-shaped, that is, the hole diameter of the stress release hole 3010 gradually decreases from the second AlGaN graded layer 303 to the buffer layer 200 side, so as to form a V-shaped hole structure. Of course, in other possible embodiments, the hole pattern of the stress relief layer may also be rectangular, trapezoidal, etc. in cross-section.
Note that the stress release holes 3010 are formed by controlling the growth conditions of the porous AlGaN layer 301 to be natural, and are not prepared by a material removal process such as etching, laser, chemical etching, or the like.
Further, the porous AlGaN layer 301 is Al with low Si content x Ga (1-x) N single-layer or multi-layer structure, wherein 0.ltoreq.x.ltoreq.1, the thickness of the porous AlGaN layer 301 is 0.01 μm-5 μm, and Si concentration is 1×10 8 /cm³-1×10 18 /cm³。
As one of themBy way of example, the thickness of the porous AlGaN layer 301 is 3 μm, and the doping concentration of Si element in the porous AlGaN layer 301 is 1×10 8 /cm³。
In the present embodiment, the first AlGaN graded layer 302 in the N-type semiconductor layer 300 is graded Al with decreasing Al composition and increasing Si doping concentration x Ga (1-x) N material, wherein the Al component x is reduced from x1 to x2 from bottom to top, x2 is more than or equal to 0.4 and less than or equal to x1 and less than or equal to 1, the Si doping concentration c is increased from c1 to c2, and the Si doping concentration c1 is 2 multiplied by 10 17 A/cm. Delta. And a Si doping concentration c2 of 5X 10 18 The thickness of the first AlGaN graded layer 302 is 2 μm.
The N electrode 800 is grown by depositing metal, and the purpose of the first AlGaN graded layer 302 adopting graded is to set the N electrode 800 at the position with the lowest potential barrier and the highest doping concentration in the N-type semiconductor, so that the ohmic contact resistance between the N electrode 800 and the first AlGaN graded layer 302 is reduced, and the ohmic contact resistance between the N electrode 800 and the N-type semiconductor layer 300 is reduced.
When the first AlGaN graded layer 302 is grown on the porous AlGaN layer 301, the material of the first AlGaN graded layer 302 is completely filled into the stress release hole 3010 of the porous AlGaN layer 301. The porous AlGaN layer 301 can release the stress of the N-type semiconductor by providing a plurality of stress release holes 3010 penetrating therethrough, so that the quality of the epitaxial layer is improved, and the first AlGaN graded layer 302 is filled into the stress release layer, so that the Si doping concentration of the N-type semiconductor layer 300 can be improved.
In contrast, the second AlGaN graded layer 303 in the N-type semiconductor layer 300 is graded Al with increasing Al composition and decreasing Si doping concentration x Ga (1-x) N material, wherein the Al component x increases from x3 to x4 from bottom to top, x3 is more than or equal to 0.4 and less than or equal to x4 and less than or equal to 1, the Si doping concentration c decreases from c3 to c4, and the Si doping concentration c3 is 5 multiplied by 10 18 The density c4 of Si doping is 2X 10 17 The thickness of the second AlGaN graded layer 303 is 2 μm.
In the present embodiment, the substrate 100 is preferably a sapphire substrate 100, i.e., al 2 O 3 A substrate 100; in other possible embodiments, the substrate 100 may be silicon carbide, silicon, aluminum nitrideAny one of gallium nitride and gallium oxide substrates.
In the present embodiment, the active region light emitting layer 400 is alternately grown Al x5 Ga 1-x5 N quantum barrier layer and Al x6 Ga 1- x6 The N quantum well layer, wherein the Al component x5 in the quantum barrier layer is larger than the Al component x6 in the quantum well layer, the Al component x5 in the well barrier layer is more than or equal to 0.5 and less than or equal to 1, and 0 < x6 < x5.
In the present embodiment, the material of the electron blocking layer 500 is Al with a trapezoidal decreasing Al composition x Ga (1-x) And N is a multi-layer structure, wherein x is more than or equal to 0 and less than or equal to 1, and the thickness is 1nm-500nm.
In the present embodiment, the material of the P-type semiconductor layer 600 is Al doped with Mg element x Ga (1-x) N single-layer or multi-layer structure, wherein x is more than or equal to 0 and less than or equal to 1, the thickness is 0.01 mu m-2 mu m, and the concentration of Mg is 1 multiplied by 10 14 /cm³-1×10 20 /cm³。
In the present embodiment, the ohmic contact layer 700 is made of Al with low content of Al element and high content of Mg element x Ga (1-x) N single-layer or multi-layer structure, wherein x is more than or equal to 0 and less than or equal to 0.3, the thickness is 1nm-500nm, and the Mg concentration is 1 multiplied by 10 18 /cm³-1×10 20 /cm³。
It should be further noted that, in this embodiment, since the ohmic contact layer 700 needs to be etched until the first AlGaN graded layer 302 is exposed to grow the N electrode 800, a portion of the ohmic contact layer 700 is removed, and a metal is deposited on the surface of the unetched region of the ohmic contact layer 700 to grow the P electrode 900. The N electrode 800 and the P electrode 900 are used for electrically connecting the uv led with a circuit, so that the uv led can be powered on to emit light of a corresponding color.
Compared with the prior art, the ultraviolet light-emitting diode shown in the embodiment is adopted, and has the beneficial effects that:
through setting the N type semiconductor layer into porous AlGaN layer 301, first AlGaN graded layer 302 and second AlGaN graded layer 303, be equipped with a plurality of stress relief holes 3010 on the porous AlGaN layer 301 to can release the stress of N type semiconductor layer 300, promote epitaxial layer quality, and be favorable to the Si atom to mix N type semiconductor after the stress of epitaxial layer obtains releasing, promote the doping efficiency and the carrier concentration of N type semiconductor layer 300, simultaneously, locate the surface of first AlGaN graded layer 302 with N electrode 800, reduced the ohmic contact resistance of N electrode 800 and N type semiconductor layer 300, in conclusion, can effectively promote ultraviolet emitting diode's luminous efficacy.
Comparative example 1
The structure of the ultraviolet light emitting diode in this embodiment is basically the same as that of the ultraviolet light emitting diode in the first embodiment, except that:
in this embodiment, the density of stress relief holes in the porous AlGaN layer is 1×10 9 /cm 2 。
Comparative example 2
The structure of the ultraviolet light emitting diode in this embodiment is basically the same as that of the ultraviolet light emitting diode in the first embodiment, except that:
in this embodiment, the density of stress relief holes in the porous AlGaN layer is 2×10 8 /cm 2 。
Comparative example 3
The structure of the ultraviolet light emitting diode in this embodiment is basically the same as that of the ultraviolet light emitting diode in the first embodiment, except that:
in this embodiment, the N-type semiconductor layer adopts an AlGaN single layer with a constant Si doping concentration, i.e., the N-type semiconductor layer has no holes and no gradual Si doping.
Comparative example 4
The structure of the ultraviolet light emitting diode in this embodiment is basically the same as that of the ultraviolet light emitting diode in the first embodiment, except that:
in this embodiment, the N-type semiconductor layer is a porous AlGaN layer and an AlGaN layer with unchanged Si doping concentration, i.e., the N-type semiconductor layer has holes and Si doping is not graded.
Comparative example 5
The structure of the ultraviolet light emitting diode in this embodiment is substantially the same as that of the ultraviolet light emitting diode in the first embodiment, except that:
in this embodiment, the N-type semiconductor layer adopts an AlGaN layer with increasing Si doping concentration and an AlGaN layer with decreasing Si doping concentration, i.e. the N-type semiconductor layer has no holes and gradually changes Si doping.
Referring to table 1, table 1 is a table of partial performance test results of the uv light emitting diodes shown in example 1 and comparative examples 1-5, and the (002) half-peak width, (102) half-peak width, the operating voltage VF4, the electro-optic conversion efficiency WPE, and the light efficiency improvement rate of the epitaxial wafer were respectively tested by XRD.
TABLE 1
The ultraviolet light emitting diode chips prepared in example 1 and comparative examples 1 to 5 using the same chip process conditions were respectively extracted 100 LED chips, tested at 120mA/60mA current, and the light efficiency improvement rate with respect to the conventional chips was measured as shown in table 1. As can be seen obviously by combining the data in table 1, the technical scheme in the embodiment of the invention can obviously improve the light efficiency, and compared with the conventional chip, the embodiment of the invention can improve the light efficiency by 2.16 percent and has good electrical properties of other items.
Example 2
Referring to fig. 2, a second embodiment of the present invention provides a method for manufacturing an ultraviolet light emitting diode, which is used for manufacturing the ultraviolet light emitting diode shown in the first embodiment, the method includes steps S10-S60, wherein:
step S10, providing a substrate and growing a buffer layer on the substrate;
wherein the substrate is sapphire substrate, namely Al 2 O 3 And a substrate on which a buffer layer is grown after the sapphire substrate is provided. Of course, the substrate may be a silicon substrate, a silicon carbide substrate, or other semiconductor substrate.
Step S20, a porous AlGaN layer with stress release holes is grown on the buffer layer based on preset growth conditions;
wherein, after the buffer layer is grown, when the porous AlGaN layer is grown, the stress release hole is naturally formed in the growth process of the porous AlGaN layer by changing the growth conditions, and the stress release hole penetrates through the porous AlGaN layer. In some preferred embodiments, the stress release holes in the porous AlGaN layer have a V-shaped structure, and penetrate through the porous AlGaN layer, and the diameters of the stress release holes decrease in sequence along the direction from the first AlGaN graded layer to the buffer layer.
The stress release holes are uniform in size, uniformly distributed in the porous AlGaN layer, and have a density of 1×10 7 /cm 2 -1×10 10 /cm 2 Preferably 5X 10 8 /cm 2 。
Step S30, sequentially growing a first AlGaN gradient layer and a second AlGaN gradient layer on the porous AlGaN layer, and controlling the first AlGaN gradient layer to fill the stress release hole to obtain an N-type semiconductor layer, wherein the first AlGaN gradient layer is a gradient AlGaN material with decreasing Al component and increasing Si doping concentration, and the second AlGaN gradient layer is a gradient AlGaN material with increasing Al component and decreasing Si doping concentration;
wherein the first AlGaN graded layer in the N-type semiconductor layer is graded Al with decreasing Al component and increasing Si doping concentration x Ga (1-x) N material, wherein the Al component x is reduced from x1 to x2 from bottom to top, x2 is more than or equal to 0.4 and less than or equal to x1 and less than or equal to 1, the Si doping concentration c is increased from c1 to c2, and the Si doping concentration c1 is 2 multiplied by 10 17 A/cm. Delta. And a Si doping concentration c2 of 5X 10 18 And/cm. Mu.m, the thickness of the first AlGaN graded layer is 2 μm. The first AlGaN graded layer is grown to be capable of completely filling the plurality of stress relief holes of the porous AlGaN layer.
In contrast, the second AlGaN graded layer in the N-type semiconductor layer is graded Al with gradually increasing Al component and gradually decreasing Si doping concentration x Ga (1-x) N material, wherein the Al component x increases from x3 to x4 from bottom to top, x3 is more than or equal to 0.4 and less than or equal to x4 and less than or equal to 1, the Si doping concentration c decreases from c3 to c4, and the Si doping concentration c3 is 5 multiplied by 10 18 The density c4 of Si doping is 2X 10 17 And/cm. Mu.m, and the thickness of the second AlGaN graded layer is 2 μm.
And after the second AlGaN graded layer is grown, the N-type semiconductor layer is prepared.
Step S40, sequentially growing an active region light-emitting layer, an electron blocking layer, a P-type semiconductor layer and an ohmic contact layer on the N-type semiconductor layer;
in the present embodiment, the active region light emitting layer is alternately grown Al x5 Ga 1-x5 N quantum barrier layer and Al x6 Ga 1-x6 The N quantum well layer, wherein the Al component x5 in the quantum barrier layer is larger than the Al component x6 in the quantum well layer, the Al component x5 in the well barrier layer is more than or equal to 0.5 and less than or equal to 1, and 0 < x6 < x5.
In this embodiment, the material of the electron blocking layer is Al with a trapezoidal decreasing Al component x Ga (1-x) And N is a multi-layer structure, wherein x is more than or equal to 0 and less than or equal to 1, and the thickness is 1nm-500nm.
In the present embodiment, the material of the P-type semiconductor layer is Al doped with Mg element x Ga (1-x) N single-layer or multi-layer structure, wherein x is more than or equal to 0 and less than or equal to 1, the thickness is 0.01 mu m-2 mu m, and the concentration of Mg is 1 multiplied by 10 14 /cm³-1×10 20 /cm³。
In the embodiment, the ohmic contact layer is Al with low content of Al element and high content of Mg element x Ga (1-x) N single-layer or multi-layer structure, wherein x is more than or equal to 0 and less than or equal to 0.3, the thickness is 1nm-500nm, and the Mg concentration is 1 multiplied by 10 18 /cm³-1×10 20 /cm³。
Step S50, etching the ohmic contact layer until the surface of the first AlGaN graded layer is exposed;
specifically, in this embodiment, the ohmic contact layer is etched by using a dry etching process, and the etching depth is from the surface to the surface of the first AlGaN graded layer, so as to expose the first AlGaN graded layer. That is, when the ohmic contact layer is etched, the P-type semiconductor layer, the electron blocking layer, the active region light emitting layer and the second AlGaN graded layer of the N-type semiconductor layer under the ohmic contact layer are etched and removed, thereby exposing the first AlGaN graded layer.
The epitaxial wafer of the ultraviolet light-emitting diode is manufactured.
And step S60, growing a P electrode on the surface of the unetched area of the ohmic contact layer, and growing an N electrode on the surface of the exposed first AlGaN graded layer to obtain the ultraviolet light emitting diode.
Specifically, in this embodiment, when a metal is deposited on the unetched ohmic contact layer by using a metal sputtering method to form a P electrode, similarly, a metal is deposited on the etched surface of the first AlGaN graded layer by using a metal sputtering method to form an N electrode.
All the ultraviolet light emitting diodes are manufactured.
Compared with the prior art, the ultraviolet light emitting diode manufacturing method has the beneficial effects that:
when the preparation method is used for preparing the ultraviolet light-emitting diode, the N-type semiconductor layer is arranged to be the porous AlGaN layer, the first AlGaN gradient layer and the second AlGaN gradient layer, and the porous AlGaN layer is provided with the stress release holes, so that the stress of the N-type semiconductor layer can be released, the quality of the epitaxial layer is improved, si atoms are doped into the N-type semiconductor after the stress of the epitaxial layer is released, the doping efficiency and the carrier concentration of the N-type semiconductor layer are improved, meanwhile, the N electrode is arranged on the surface of the first AlGaN gradient layer, the ohmic contact resistance of the N electrode and the N-type semiconductor layer is reduced, and the luminous efficiency of the ultraviolet light-emitting diode can be effectively improved.
In the description of the present specification, a description referring to terms "one embodiment," "some embodiments," "examples," "specific examples," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiments or examples. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
The foregoing examples illustrate only a few embodiments of the invention, and are described in detail, but are not to be construed as limiting the scope of the invention. It should be noted that it is possible for those skilled in the art to make several variations and modifications without departing from the spirit of the invention, which are all within the scope of the invention. Accordingly, the scope of protection of the present invention is to be determined by the appended claims.
Claims (8)
1. The utility model provides an ultraviolet emitting diode, includes from bottom to top stacks gradually the substrate that sets up, buffer layer, N type semiconductor layer, active region luminescent layer, electron blocking layer, P type semiconductor layer, ohmic contact layer, N electrode and P electrode, its characterized in that:
the N-type semiconductor layer comprises a porous AlGaN layer, a first AlGaN gradient layer and a second AlGaN gradient layer which are sequentially laminated on the buffer layer, a stress release hole is formed in the porous AlGaN layer, the first AlGaN gradient layer is made of a gradient AlGaN material with gradually decreasing Al component and gradually increasing Si doping concentration, the stress release hole of the porous AlGaN layer is filled, the second AlGaN gradient layer is made of a gradient AlGaN material with gradually increasing Al component and gradually decreasing Si doping concentration, and the N electrode is laminated on one side surface of the first AlGaN gradient layer, which is far away from the porous AlGaN layer;
wherein the stress release holes are formed naturally by controlling the growth conditions of the porous AlGaN layer, the stress release holes are multiple, the size of each stress release hole is consistent, the stress release holes are uniformly distributed in the porous AlGaN layer, and the density of the stress release holes in the porous AlGaN layer is 1 multiplied by 10 7 /cm 2 -1×10 10 /cm 2 。
2. The ultraviolet light emitting diode of claim 1, wherein the stress relief holes are disposed through the porous AlGaN layer.
3. The uv led of claim 2, wherein the stress relief holes are V-shaped and the aperture decreases in sequence in the direction from the first AlGaN graded layer to the buffer layer.
4. The ultraviolet light-emitting diode according to claim 1, wherein the porous AlGaN layer is low Si element doped Al x Ga (1-x) N single-layer or multi-layer structure, wherein x is more than or equal to 0 and less than or equal to 1, the thickness of the porous AlGaN layer is 0.01 mu m-5 mu m, and the Si concentration is 1 multiplied by 10 8 /cm³-1×10 18 /cm³。
5. The ultraviolet light-emitting diode according to claim 1, wherein the first AlGaN graded layer is graded Al with decreasing Al composition and increasing Si doping concentration x Ga (1-x) N material, wherein Al component x decreases from x1 to x2 from bottom to top, si doping concentration c increases from c1 to c2, x2 is more than or equal to 0.4 and less than or equal to x1 and less than or equal to 1, thickness is 1 μm-3 μm, si doping concentration c1 is 2×10 17 A/cm. Delta. And a Si doping concentration c2 of 5X 10 18 /cm³。
6. The ultraviolet light-emitting diode according to claim 1, wherein the second AlGaN graded layer is graded Al with increasing Al composition and decreasing Si doping concentration x Ga (1-x) N material, wherein the Al component x increases from x3 to x4 from bottom to top, the Si doping concentration c decreases from c3 to c4, x3 is more than or equal to 0.4 and less than or equal to x4 and less than or equal to 1, the thickness is 1 mu m-3 mu m, and the Si doping concentration c3 is 5 multiplied by 10 18 The density c4 of Si doping is 2X 10 17 /cm³。
7. A method for producing an ultraviolet light emitting diode, wherein the method is used for producing the ultraviolet light emitting diode according to any one of claims 1 to 6, the method comprising:
providing a substrate and growing a buffer layer on the substrate;
growing a porous AlGaN layer with stress release holes on the buffer layer based on preset growth conditions;
sequentially growing a first AlGaN gradient layer and a second AlGaN gradient layer on the porous AlGaN layer, and controlling the first AlGaN gradient layer to fill the stress release hole to obtain an N-type semiconductor layer, wherein the first AlGaN gradient layer is a gradient AlGaN material with gradually decreasing Al component and gradually increasing Si doping concentration, and the second AlGaN gradient layer is a gradient AlGaN material with gradually increasing Al component and gradually decreasing Si doping concentration;
sequentially growing an active region light-emitting layer, an electron blocking layer, a P-type semiconductor layer and an ohmic contact layer on the N-type semiconductor layer;
etching the ohmic contact layer until the surface of the first AlGaN graded layer is exposed;
growing a P electrode on the surface of the unetched area of the ohmic contact layer, and growing an N electrode on the surface of the exposed first AlGaN graded layer to obtain an ultraviolet light emitting diode;
wherein the stress release holes are formed naturally by controlling the growth conditions of the porous AlGaN layer, the stress release holes are multiple, the size of each stress release hole is consistent, the stress release holes are uniformly distributed in the porous AlGaN layer, and the density of the stress release holes in the porous AlGaN layer is 1 multiplied by 10 7 /cm 2 -1×10 10 /cm 2 。
8. The method according to claim 7, wherein in the step of growing a porous AlGaN layer having a stress release hole on the buffer layer based on a preset growth condition, the stress release hole is provided through the porous AlGaN layer and has a V-shaped structure, and the aperture is sequentially decreased in a direction from the first AlGaN graded layer to the buffer layer.
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