CN114843379A - Light-emitting diode structure based on patterned nitride single crystal substrate and preparation method - Google Patents
Light-emitting diode structure based on patterned nitride single crystal substrate and preparation method Download PDFInfo
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Abstract
The application discloses a light-emitting diode structure based on a patterned nitride single crystal substrate and a preparation method thereof. The light-emitting diode structure comprises a nitride single crystal substrate, a nitride layer, a filling layer and a light-emitting epitaxial layer; a plurality of regular pattern structures are formed on the surface of the substrate, and the pattern structures are raised or recessed relative to the surface of the nitride single crystal substrate; the nitride layer is continuously and conformally covered on the pattern structures, and the pattern structures and the nitride layer are matched to form a reflecting structure which at least can reflect light emitted by the light-emitting epitaxial layer; the surface of the filling and leveling layer is smooth and continuously covered on the nitride layer; the light emitting epitaxial layer is grown on the filling and leveling layer. The light-emitting diode structure has the advantages of low electric leakage, long service life, high luminous efficiency, high luminous uniformity and the like, can realize high-brightness and high-efficiency LED devices, and has good application prospect in the high-end application field.
Description
Technical Field
The application relates to a Light Emitting Diode (LED) structure, in particular to a light emitting diode structure based on a patterned nitride single crystal substrate and a preparation method thereof, and belongs to the technical field of semiconductors.
Background
GaN-based LEDs based on Patterned Sapphire Substrates (PSS) have been widely used because of their high brightness and other characteristics. By adopting the patterned sapphire substrate, on one hand, the mode of growing the GaN material on the patterned sapphire substrate can be changed from longitudinal epitaxy to transverse epitaxy, so that the dislocation density of the GaN epitaxial material can be effectively reduced, further the non-radiative recombination of an active region is reduced, the reverse leakage current is reduced, and the service life of an LED is prolonged; on the other hand, the light emitted by the active region can be scattered by the interface of the GaN epitaxial material and the sapphire substrate for multiple times, the emergence angle of total reflection light is changed, and the emergence probability of the light of the flip LED from the sapphire substrate is increased, so that the light extraction efficiency is improved, and the brightness of the emergent light of the LED is greatly improved.
In recent years, GaN single crystal substrates have been favored because of their advantages such as ultra-low dislocation density and ultra-high crystal quality. The GaN material growing on the GaN single crystal substrate belongs to homoepitaxy, so that the high LED epitaxial crystal quality can be obtained, but no interface reflection is formed in the LED, and the light emitting efficiency is improved by no multi-angle reflection, so that the light emitting efficiency of the GaN homoepitaxy LED is inferior to that of the LED growing on the patterned sapphire substrate.
Disclosure of Invention
The present application is directed to a light emitting diode structure based on a patterned nitride single crystal substrate and a method for manufacturing the same, so as to overcome the disadvantages of the prior art.
In order to achieve the above purpose, the present application adopts a technical solution comprising:
one aspect of the present application provides a light emitting diode structure based on a patterned nitride single crystal substrate, comprising:
a nitride single crystal substrate having a plurality of regular pattern structures formed on a surface thereof, the pattern structures being raised or depressed with respect to the surface of the nitride single crystal substrate;
the nitride layer is continuously and conformally covered on the plurality of pattern structures and is matched with the plurality of pattern structures to form a reflecting structure, and the reflecting structure at least can reflect light emitted by the light-emitting epitaxial layer;
the filling and leveling layer continuously covers the nitride layer, and the surface of the filling and leveling layer is smooth; and
and the light-emitting epitaxial layer is grown on the filling and leveling layer.
Another aspect of the present application provides a method for preparing a light emitting diode structure based on a patterned nitride single crystal substrate, which includes:
processing a plurality of regular pattern structures on the surface of the nitride single crystal substrate, wherein the pattern structures are raised or recessed relative to the surface of the nitride single crystal substrate;
forming a nitride layer on the plurality of pattern structures, enabling the nitride layer to continuously and conformally cover the plurality of pattern structures, enabling the nitride layer to be matched with the plurality of pattern structures to form a reflecting structure, and enabling the reflecting structure to at least reflect light emitted by the light-emitting epitaxial layer;
growing a filling layer with a smooth surface on the nitride layer; and
and growing a light-emitting epitaxial layer on the filling layer.
According to the method, the plurality of regular pattern structures are formed on the surface of the nitride single crystal substrate and can be used as the interface layer of the nitride single crystal substrate and the nitride material, so that light emitted by the active region is scattered for many times through the interface layer, the emergence angle of total reflection light is changed, and the light extraction efficiency is improved; meanwhile, a nitride layer, particularly an A1-containing nitride layer, grows on the pattern structure, so that the pattern structure and the nitride layer are matched to form a light reflection interface with larger area and better continuity, light emitted by the light-emitting epitaxial layer is reflected more efficiently, the light extraction efficiency of the device is obviously improved, and meanwhile, the nitride layer can be used for blocking and inhibiting dislocation of a nitride single crystal substrate, so that the quality of epitaxial crystals is further improved; and then, a flat GaN material layer is formed through the growth of the filling layer, so that the high-brightness homogeneous nitride LED can be realized.
Compared with the prior art, the technical scheme of the application not only gives full play to the advantages of homoepitaxy, enables the epitaxial structure of the light-emitting diode to have ultrahigh crystal quality, ensures that the light-emitting diode has the characteristics of low electric leakage, long service life and the like, but also obviously improves the light-emitting efficiency and the light-emitting uniformity of the light-emitting diode, realizes a light-emitting diode device with high brightness and high efficiency, and has good application prospect in the high-end application field.
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In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
Fig. 1 is a schematic diagram of a light emitting diode structure based on a patterned nitride single crystal substrate in a first embodiment of the present application;
FIG. 2 is an enlarged partial schematic view of portion A of FIG. 1;
FIG. 3 is a schematic flow chart of a process for preparing a light emitting diode structure based on a patterned nitride single crystal substrate according to the present application;
fig. 4 is a schematic diagram of a light emitting diode structure based on a patterned nitride single crystal substrate in a second embodiment of the present application;
fig. 5 is a partially enlarged schematic view of a portion B in fig. 4.
Detailed Description
As described above, LEDs formed by homoepitaxy on GaN single crystal substrates are often inferior to LEDs based on patterned sapphire substrates in terms of light extraction efficiency, and existing schemes for increasing light extraction efficiency of GaN homoepitaxy LEDs have some defects. In view of the above, after a great deal of research and experiments, the applicant has proposed the technical solution of the present application, which will be described in more detail below.
Some embodiments of the present application provide a light emitting diode structure based on a patterned nitride single crystal substrate comprising:
a nitride single crystal substrate having a plurality of regular pattern structures formed on a surface thereof, the pattern structures being raised or depressed with respect to the surface of the nitride single crystal substrate;
the nitride layer is continuously and conformally covered on the plurality of pattern structures and is matched with the plurality of pattern structures to form a reflecting structure, and the reflecting structure at least can reflect light emitted by the light-emitting epitaxial layer;
the filling and leveling layer continuously covers the nitride layer, and the surface of the filling and leveling layer is smooth; and
and the light-emitting epitaxial layer is grown on the filling and leveling layer.
According to the method, the pattern structure is formed on the surface of the nitride single crystal substrate, the nitride layer is covered on the pattern structure, the appearance of the pattern structure is continued by the nitride layer, on one hand, dislocation of the nitride single crystal can be filtered by the pattern structure, on the other hand, the pattern structure and the nitride layer can be matched to form a light reflection interface with larger area and better continuity, light emitted by the light-emitting epitaxial layer is reflected more efficiently, the light extraction efficiency of the device is remarkably improved, meanwhile, the nitride layer can be used for blocking and inhibiting dislocation of the nitride single crystal substrate, the epitaxial crystal quality is further improved, and finally obtained devices are further improved in the aspects of reverse leakage current, service life and other performances.
In the present application, the pattern structure may be formed by physically and/or chemically processing the surface of the nitride single crystal substrate, and may be closely arranged or dispersed on the surface of the nitride single crystal substrate, and may have a certain repetition period. And the shape, size, spacing, etc. of the pattern structure can be adjusted according to the requirements of practical application.
In one embodiment, the pattern structure includes a funnel-shaped or inverted pyramid-shaped pit, such as a V-shaped pit, formed on the surface of the nitride single crystal substrate, and compared with pattern structures of other shapes, on one hand, the sidewall of the V-shaped pit covering the nitride layer can increase total reflection, thereby further increasing light reflection efficiency, and on the other hand, the inside of the V-shaped pit can induce lateral growth, thereby improving dislocation filtering efficiency, and being more beneficial to improving the quality of homoepitaxial crystal, and meanwhile, the pattern structure can be more easily manufactured by means of dry etching, wet etching and the like, and the process is more controllable.
Further, the opening angle of the pit may be 15 to 75 °, the depth may be 100nm to 10 μm, and the opening diameter may be 10nm to 1 μm. If the pit size is too small, it is difficult to achieve the aforementioned effects of increasing the light reflection efficiency and improving the dislocation filtering efficiency, whereas if the pit size is too large, it may cause unevenness in subsequent epitaxial growth and deterioration in crystal quality.
Further, the pitch of two adjacent pits may be 1 μm to 10 μm. If the distance between adjacent pits is too large, the positive effects on the light reflection efficiency, the dislocation filtering efficiency, and the like are greatly suppressed, and if the distance between adjacent pits is too small, that is, the pit arrangement is too dense, the quality of the nitride single crystal substrate itself and the epitaxial structure is adversely affected.
In one embodiment, the nitride layer is an Al-containing nitride layer, and the trend of the variation of at least one of the opening angle, the opening diameter and the depth of the pit is inversely related to the trend of the Al content in the nitride layer, i.e., the higher the Al composition of the nitride layer, the shallower the depth of the pit, the smaller the opening, and the smaller the spacing, thereby facilitating a1 migration, which is beneficial for the growth of the nitride layer and the fill-up layer.
In one embodiment, the nitride layer has a first region and a second region, wherein the first region is disposed corresponding to the pattern structure, and the second region is disposed corresponding to a region between adjacent pattern structures; the thickness of the second region is smaller than the average thickness of each region of the nitride layer, and/or a coarsening structure is formed on the surface of the second region.
Preferably, the thickness of the second region is from 100nm to 150 nm.
Preferably, the roughness Ra value of the surface of the second region is more than 0.1 μm, and preferably 0.1 μm to 0.9 μm.
The dislocation density in the epitaxial structure grown subsequently can be further reduced by thinning the nitride layer part region at the adjacent pit spacing position (namely the second region), and the whole nitride layer is prevented from being too thin; it should be noted that the nitride layer at these locations should not be too thin to cause voids during subsequent epitaxial growth at elevated temperatures. The thickness of the second region is set to be smaller than the average thickness of the respective regions of the nitride layer, preferably 100nm to 150 nm.
The nitride layer part area at the position of the adjacent pit interval is subjected to surface roughening treatment, so that the light original path reflected by the light reflection interface can be effectively prevented from returning to the active area, the absorption of the nitride single crystal substrate to light is reduced, and the light extraction efficiency of the device is effectively improved.
When the second area is processed by adopting the thinning and surface roughening modes, the advantages of the two modes can be fully exerted, and especially, the light effect improvement effect is more remarkable for Micro LEDs, Mini LEDs and other Micro LEDs.
In one embodiment, the fill-up layer includes a nucleation layer, a 3D layer, and a merged layer sequentially grown on the nitride layer.
The thickness of the nucleation layer may be 0to 50nm, and the nucleation layer may not be provided depending on the material and size of the nitride layer.
Wherein the thickness of the 3D layer may be 300nm to 800 nm.
Wherein the thickness of the combined layer may be 500nm to 1500 nm.
In one embodiment, the material of the nitride layer includes InAlN or AlN, and the like, and is not limited thereto. Preferably, the nitride layer is lattice-matched to the nitride single crystal substrate. Compared with other materials such as aluminum oxide, silicon oxide and the like, the InAlN, AlN and the like are the same as or similar to the nitride single crystal substrate, are very stable at the epitaxial growth temperature, can be always firmly combined with the nitride single crystal substrate, and can more effectively ensure the uniformity of epitaxial growth and the crystal quality.
In one embodiment, the thickness of the nitride layer is 50nm-500nm, and if the thickness is too thin, the nitride layer is easily decomposed to form holes during the temperature rising process, which is not favorable for the continuity of the interface; however, if it is too thick, it will result in an increase in stress and affect the crystal quality of the epitaxial structure to some extent which is grown later, and of course, the effect is relatively small in consideration of the high crystal quality of the nitride single crystal substrate. Preferably, the thickness of the nitride layer is 100nm to 200 nm.
In the present application, the group III nitride single crystal substrate may be a GaN single crystal substrate, an AlN single crystal substrate, or the like, and is not limited thereto. Further, the group III nitride single crystal substrate may be n-type doped, p-type doped, or undoped.
In one embodiment, the light emitting epitaxial layer includes a first semiconductor layer of a first conductivity type, a quantum well active region, and a second semiconductor layer of a second conductivity type sequentially grown on the filling layer.
Wherein said first conductivity type may be n-type and correspondingly the second conductivity type is p-type and vice versa.
The materials of the first semiconductor layer, the active region and the second semiconductor layer may be selected from group III-V compounds, such as group III nitrides, e.g., GaN, InGaN, AIInGaN, etc., but are not limited thereto.
For example, the first semiconductor layer may be an N-type layer, which may further include a highly doped N-type GaN layer, an N — Al electron extension layer, a low doped N-type GaN layer, and the like.
For example, the quantum well active region may include a Multiple Quantum Well (MQWs) light emitting layer, etc., and is not limited thereto. For example, the quantum well active region may comprise InGaN or the like. More specifically, the quantum well active region may be a multiple quantum well light emitting layer composed of multiple InGaN quantum wells and multiple GaN quantum barriers which are alternately grown. Further, the quantum well active region may specifically include an SRL stress release layer, a shadow quantum well structure, a light emitting quantum well structure, and the like.
For example, the second semiconductor layer may be a P-type layer, which may further include a low temperature P-type layer, an EBL electron blocking layer, a high temperature P-type layer, and the like.
Some embodiments of the present application provide a method of preparing the patterned nitride single crystal substrate-based light emitting diode structure, including:
processing a plurality of regular pattern structures on the surface of the nitride single crystal substrate, wherein the pattern structures are raised or recessed relative to the surface of the nitride single crystal substrate;
forming a nitride layer on the plurality of pattern structures, enabling the nitride layer to continuously and conformally cover the plurality of pattern structures, enabling the nitride layer to be matched with the plurality of pattern structures to form a reflecting structure, and enabling the reflecting structure to at least reflect light emitted by the light-emitting epitaxial layer;
growing a filling layer with a smooth surface on the nitride layer; and
and growing a light-emitting epitaxial layer on the filling layer.
In the present application, the shape, size, arrangement, and spacing of the pattern structures may be as described above, and are not described herein again.
In one embodiment, the preparation method specifically comprises: and etching the surface of the nitride single crystal substrate in a dry etching and/or wet etching mode to form the pattern structure.
Wherein, the surface of the nitride single crystal substrate may refer to a nitrogen plane or a gallium plane of the nitride single crystal substrate. The nitride single crystal substrate has very active chemical property of a nitrogen surface, and is more easily corroded and etched compared with a gallium surface under the same condition, so that the nitride single crystal substrate can be subjected to soaking corrosion by using a chemical solution by using wet etching which is simple and easy to operate to form the pattern structure. Suitable chemical solutions may include potassium hydroxide solution, phosphoric acid solution, NH 4 OH/H 2 O 2 Mixed solution, etc., without being limited thereto. The wet etching may be performed at room temperature or under heating. Of course, the gallium face of the nitride single crystal substrate may be subjected to dry etching or the like to form the aforementioned pattern structure.
In one embodiment, the preparation method comprises the following steps: the nitride layer is formed using an Al-containing nitride, and at least one of an opening angle, an opening diameter, and a depth of the pit is decreased or increased as an Al content in the nitride layer increases or decreases, respectively.
In one embodiment, the preparation method further comprises:
defining a first area and a second area in the nitride layer, wherein the first area is arranged corresponding to the pattern structures, and the second area corresponds to the area between the adjacent pattern structures; and
and thinning the second region of the nitride layer until the thickness of the second region is smaller than the average thickness of each region of the nitride layer, and/or roughening the surface of the second region of the nitride layer until the roughness Ra value of the surface of the second region is larger than 0.1 μm, preferably 0.1 μm-0.9 μm.
The thinning process may be implemented by CMP (chemical mechanical polishing) or other physical and chemical means, and the thinning amplitude may be as described above.
The roughening treatment may be achieved by the aforementioned dry etching, wet etching, and the like, and the finally formed roughened structure may be as described above.
In one embodiment, the preparation method specifically comprises: growing a nucleation layer, a 3D layer, and a merged layer on the nitride layer in sequence, thereby forming the fill-and-level layer. Wherein, whether to grow the nucleation layer can be determined according to the material, thickness, etc. of the nitride layer. The 3D layer is a three-dimensional longitudinal growth mode, the height depending on the height of the pattern structure. The merged layer is a two-dimensional lateral growth mode that eventually fills in the pattern structure, forming a planar semiconductor material layer.
In one embodiment, the preparation method specifically comprises: and sequentially growing a first semiconductor layer of a first conduction type, a quantum well active region and a second semiconductor layer of a second conduction type on the filling layer so as to form the light-emitting epitaxial layer.
The material and thickness of the nitride layer, the material of the nitride single crystal substrate, the structure and material of the light-emitting epitaxial layer, and the like are as described above.
In the present application, the fill-up layer and each semiconductor material layer in the light-emitting epitaxial layer may be grown by using HVPE (hydride vapor phase epitaxy), MOCVD (metal organic chemical vapor deposition), PECVD (plasma enhanced chemical vapor deposition), and the like, and are not limited thereto.
In the present application, the nitride layer may also be formed by physical and/or chemical vapor deposition, such as sputtering, MOCVD, ALD, PEDCVD, and the like, without being limited thereto.
In one embodiment, the growth of the nitride layer, the filling layer and the light emitting epitaxial layer can be continuously completed in the same epitaxial growth equipment, so as to further reduce the influence of the external environment on the quality of the device and obtain a light emitting diode structure with more excellent performance.
Referring to fig. 1-2, in a first embodiment of the present application, a light emitting diode structure based on a patterned nitride single crystal substrate includes:
a nitride single crystal substrate 1, a plurality of regular pattern structures are formed on the surface of the substrate, and the pattern structures can be V-shaped pits 11, and a plurality of V-shaped pits are arranged in an array;
the nitride layer 2 continuously and conformally covers the plurality of pattern structures and is matched with the plurality of pattern structures to form a reflecting structure, the reflecting structure can reflect light emitted by the light-emitting epitaxial layer, and the nitride layer is matched with the crystal lattices of the nitride single crystal substrate;
a filling-up layer 3 continuously covering the nitride layer and having a flat surface, wherein the filling-up layer 3 comprises a nucleation layer 31, a 3D layer 32 and a merging layer 33 which are formed by growth in sequence; and
and a light emitting epitaxial layer 4 grown on the filling level layer and including an N-type region 41 (i.e., the first semiconductor layer), a quantum well active region 42, and a P-type region 43 (i.e., the second semiconductor layer) which are sequentially grown. Each of N-type region 41, quantum well active region 42, and P-type region 43 may further comprise other further structural layers known to those skilled in the art, which are not shown here.
With continued reference to fig. 3, a method for fabricating the led structure includes:
firstly, etching the surface of the GaN single crystal substrate 1 to form a plurality of regular pattern structures, and obtaining the patterned GaN single crystal substrate. The morphology, size, pitch, etc. of the pattern structure may be as described above, and may be, for example, V-shaped pits with an opening angle α of 15 to 75 °, a depth d of 100nm to 10 μm, an opening diameter r of 10nm to 1 μm, and a pitch L of adjacent V-shaped pits of 1 μm to 10 μm. The adopted etching mode can be wet etching or dry etching.
Then, the patterned GaN single crystal substrate is placed into a sputtering system or other physical/chemical vapor deposition systems to deposit a nitride layer 2, wherein the material of the nitride layer is preferably InAlN, AlN and the like, and the thickness of the nitride layer can be 50nm-500nm, preferably 100nm-200 nm;
and then, carrying out MOCVD epitaxial process, sequentially growing a nucleation layer, a 3D layer and a merging layer on the surface of the patterned GaN single crystal substrate to form a filling layer 3, and then sequentially growing an N-type region, a quantum well active region and a P-type region on the filling layer to form a light-emitting epitaxial layer 4, thereby finally obtaining the light-emitting diode structure with high light-emitting efficiency based on GaN homoepitaxy.
The method provided in the exemplary embodiment is also applicable to the production of a light emitting diode structure based on an AlN single crystal substrate, and the like.
According to the preparation method, the pattern structure is formed by etching on the nitride single crystal substrate, dislocation of the nitride single crystal substrate can be filtered, the nitride layer is deposited and continues the pattern structure, the nitride layer can be matched with the pattern structure to form a continuous light reflection interface with a larger area, the reflection effect is achieved, the lattice matching performance of the nitride layer and the nitride single crystal substrate is better, and dislocation of the nitride single crystal substrate can be blocked and inhibited.
In a second embodiment of the present application, a light emitting diode structure based on a patterned nitride single crystal substrate is shown in fig. 4-5, which is substantially the same as the light emitting diode structure shown in fig. 1, except that the surface of the region of the nitride layer 2 corresponding to the adjacent pit spacing locations is formed with a roughened structure 21 to further improve the light extraction efficiency, and the principle is as described above. Moreover, the roughened structure 21 is more favorable for the growth of the nucleation layer 31 in the filling layer 3.
In some alternatives, the regions of the nitride layer 2 corresponding to the adjacent pit-spacing locations may also be thinned, or both thinned and formed with a roughened structure, with the advantages described above.
Accordingly, a method for fabricating the led structure can also be seen in fig. 3, but after forming the nitride layer and before growing the filling layer, it is necessary to perform a thinning process and/or a surface roughening process on the region of the nitride layer corresponding to the location of the adjacent pit spacing.
Some embodiments of the present application also provide a light emitting diode, comprising:
the LED structure based on the patterned nitride single crystal substrate; and
and the electrode is matched with the light-emitting diode structure.
In one embodiment, the electrodes may include a first electrode, a second electrode, etc. that cooperates with the light emitting diode structure. For example, the first electrode is an N electrode, the second electrode is a P electrode, or vice versa. The arrangement of the electrodes is well known in the art and will not be described herein.
The technical solutions of the present application will be described in more detail below with reference to the accompanying drawings and several examples, but it should be understood that the following examples are only for explaining and illustrating the technical solutions, but do not limit the scope of the present application. Further, unless otherwise specified, various raw materials, reaction equipment, detection equipment, methods, and the like used in the following examples are known in the art.
A method for preparing the light-emitting diode structure comprises the following steps:
s1, placing the GaN single crystal substrate into an Inductively Coupled Plasma (ICP) etching device, etching the surface of the GaN single crystal substrate to form uniform and regular V-shaped pits, wherein the opening angle of each V-shaped pit is about 60 degrees, the depth of each V-shaped pit is about 0.5 mu m, the opening diameter of each V-shaped pit is about 0.1 mu m, and the distance between every two adjacent V-shaped pits is about 0.5 mu m, so that the patterned substrate is obtained.
S2, placing the patterned substrate processed in the step S1 into a Physical Vapor Deposition (PVD) device, and depositing AlN with the thickness of about 150nm at 500 ℃ to uniformly cover the surface of the patterned substrate.
S3, placing the patterned substrate with the AlN layer covered on the surface after being processed in the step S2 into a Metal Organic Chemical Vapor Deposition (MOCVD) system, heating to about 1020 ℃, controlling the thickness to about 1.2 mu m, heating to about 1080 ℃, reducing the pressure to about 200torr, introducing a TMGa source after annealing for about 5 minutes, performing three-dimensional longitudinal growth of GaN under the condition that V/III is 800, controlling the thickness to about 1.2 mu m, controlling the thickness to about 1 mu m, and ensuring that the surface is completely combined and the GaN material layer is flat. Then, the temperature is reduced to about 1050 ℃, and the growth of an N-type region is carried out, wherein the N-type region comprises Si doped 1E19cm with the thickness of about 2 mu m -3 Of N-type GaN, Si-doped 2E18cm with a thickness of about 100nm -3 N-type AlGaN and Si doped 1E17cm with thickness of about 200nm -3 The N-type GaN layer of (1). Then cooling to 880 ℃, and growing an SRL stress release layer, wherein the structure is InGaN/GaN circulation, and the total thickness is controlled to be about 150 nm; continuously cooling to about 805 ℃ to grow the shadow quantum well, wherein the total thickness of the 6 pairs of InGaN/GaN structures is about 72 nm; then cooling to about 780 ℃ to grow a luminescent quantum well, wherein the total thickness of 10 pairs of InGaN/GaN structures is about 150 nm; at this temperature, the growth enters the P-type region, firstly, the low-temperature P-type GaN is grown, and the Mg doping concentration is 2E20cm -3 The thickness is about 10nm, and the temperature is raised to about 980 ℃ to grow the EBL electron blocking layerP-type AlGaN layer with Mg doping concentration of 5E19cm -3 About 20nm thick, and finally growing high-temperature P-type GaN with Mg doping concentration 2E20cm -3 And the thickness is about 50 nm. The finally obtained led structure may be named sample B.
Comparative example 1 this comparative example provides a GaN single crystal substrate-based light emitting diode structure similar to that of example 1, except that: the GaN single crystal substrate surface was flat and not patterned.
A method of preparing the light emitting diode structure is substantially the same as that of example 1 except that: step S1 is omitted, and in step S2, an AlN layer is directly deposited on the surface of the GaN single crystal substrate that has not been subjected to patterning. The finally obtained led structure may be named sample a. The AlN layer and the epitaxial structure of sample A, B were grown in the same furnace.
Sample A, B was tested for photoluminescence PL and the results are shown in table 1 below. For the sample B, the surface of the sample B is subjected to patterning treatment and the nitride layer is added, so that the emergence angle of emergent light reflected to the substrate surface is changed, the light emergence effect is obviously increased, the emergence angle of the emergent light reflected to the substrate is changed, the light emergence effect is obviously increased, and the actually obtained photoluminescence intensity is about 60% higher than that of the sample A.
Comparative example 2 this comparative example provides a light emitting diode structure based on a GaN single crystal substrate and a method of manufacturing the same that are substantially the same as sample B except that: the AlN layer is omitted. The light emitting diode structure of this comparative example may be designated sample C.
Comparative example 3 this comparative example provides a light emitting diode structure based on a GaN single crystal substrate and a method of manufacturing the same that are substantially the same as sample B except that: the AlN layer is adjusted to have a thickness of about 20 nm. The light emitting diode structure of this comparative example may be designated sample D.
Comparative example 4 this comparative example provides a light emitting diode structure based on a GaN single crystal substrate and a method of manufacturing the same that are substantially the same as sample B except that: the AlN layer is adjusted to have a thickness of about 600 nm. The light emitting diode structure of this comparative example may be designated sample E.
Comparative example 5 this comparative example provides a light emitting diode structure based on a GaN single crystal substrate and a method of manufacturing the same that are substantially the same as sample B except that: the opening angle of the V-shaped pit is adjusted to about 85 DEG, the opening diameter is adjusted to about 1.5 mu m, the depth is adjusted to about 1.2 mu m, and the pitch of the adjacent V-shaped pits is adjusted to about 2 mu m. The light emitting diode structure of this comparative example may be designated sample F.
Comparative example 6 this comparative example provides a light emitting diode structure based on a GaN single crystal substrate and a method of manufacturing the same that are substantially the same as sample B except that: the opening angle of the V-shaped pit is adjusted to about 60 degrees, the opening diameter is adjusted to about 50nm, the depth is adjusted to about 30nm, and the distance between the adjacent V-shaped pits is adjusted to about 10 nm. The light emitting diode structure of this comparative example may be designated sample G.
Comparative example 7 this comparative example provides a light emitting diode structure based on a GaN single crystal substrate and a method of manufacturing the same that are substantially the same as sample B except that: the uniformly arranged V-shaped pits are replaced by a plurality of uniformly arranged Mongolian yurt-shaped bulges, the bottom width of each bulge is about 2.7 mu m, the height of each bulge is about 1.6 mu m, and the distance between every two adjacent bulges is about 0.3 mu m. The light emitting diode structure of this comparative example may be designated as sample H.
Example 2 this example provides a light emitting diode structure based on GaN single crystal substrate and a method for making the same that are substantially the same as sample B, except that: the AlN layer was thinned in a region corresponding to the position of the spacing between adjacent pits to a thickness of about 100 nm. The thinning treatment is realized by a chemical mechanical polishing mode. After the thinning treatment is finished, the growth of the filling and leveling layer and the growth of the light-emitting epitaxial layer are sequentially carried out. The led structure of this example can be named sample I.
Example 3 this example provides a light emitting diode structure based on GaN single crystal substrate and a method for making the same that are substantially the same as sample B, except that: the AlN layer is surface-roughened in regions corresponding to the locations of adjacent pit spaces. The surface roughening treatment specifically comprises the following steps: after the AlN layer is formed, the surface of the area corresponding to the interval position between adjacent pits in the AlN layer is corroded for about 5min by NaOH solution with the concentration of about 2mol/L, and then the AlN layer is cleaned, dried and then a filling layer and a luminous epitaxial layer are sequentially grown. The led structure of this example can be named sample J.
Example 4 this example provides a light emitting diode structure based on GaN single crystal substrate and its preparation method that is substantially the same as sample K, except that: the AlN layer is thinned to a thickness of about 100nm in the area corresponding to the interval position between adjacent pits, and then is subjected to surface roughening treatment. After the surface roughening treatment is finished, the growth of the filling layer and the growth of the light-emitting epitaxial layer are sequentially carried out. The led structure of this example can be named sample K.
The properties of the samples A to L were measured, and the results are shown in Table 1.
TABLE 1 results of Performance testing of sample A-sample L
Example 5 this example provides a GaN single crystal substrate-based light emitting diode structure and method of fabrication substantially the same as example 1, but wherein the nitride layer is an AlN layer having a thickness of about 200 nm.
Example 6 this example provides a GaN single crystal substrate-based light emitting diode structure and a method of fabricating the same as example 1, but wherein the nitride layer is an AlN layer having a thickness of about 50 nm.
Embodiment 7 this example provides a light emitting diode structure based on GaN single crystal substrate and a method for fabricating the same as embodiment 1, but the nitride layer is InAlN layer with a thickness of about 500 nm.
The device of example 5 has performance similar to sample B in terms of light extraction efficiency and light extraction uniformity. The devices of examples 6 to 7 also had higher light-emitting efficiency and light-emitting uniformity, but were inferior to the devices of examples 1 to 5 in these properties.
Finally, it should be noted that: although the present application has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that modifications may be made to the embodiments or portions thereof without departing from the spirit and scope of the present application.
Claims (10)
1. A light emitting diode structure based on a patterned nitride single crystal substrate, comprising:
a nitride single crystal substrate having a plurality of regular pattern structures formed on a surface thereof, the pattern structures being raised or depressed with respect to the surface of the nitride single crystal substrate;
the nitride layer is continuously and conformally covered on the plurality of pattern structures and is matched with the plurality of pattern structures to form a reflecting structure, and the reflecting structure at least can reflect light emitted by the light-emitting epitaxial layer;
the filling and leveling layer continuously covers the nitride layer, and the surface of the filling and leveling layer is smooth; and
and the light-emitting epitaxial layer is grown on the filling and leveling layer.
2. The patterned nitride single crystal substrate-based light emitting diode structure of claim 1, wherein: the pattern structure comprises funnel-shaped or inverted pyramid-shaped pits formed on the surface of the nitride single crystal substrate; the opening angle of the pits is 15-75 degrees, the depth is 100nm-10 mu m, the opening diameter is 10nm-1 mu m, and the distance between two adjacent pits is 1 mu m-10 mu m; and/or the thickness of the nitride layer is 50-500 nm;
and/or the nitride layer is an Al-containing nitride layer, and the trend of at least one of the opening angle, the opening diameter and the depth of the pit is inversely correlated with the trend of the Al content in the nitride layer.
3. The patterned nitride single-crystal substrate-based light-emitting diode structure according to claim 1, characterized in that: the nitride layer has a first region and a second region, wherein the first region is disposed corresponding to the pattern structure, and the second region is disposed corresponding to a region between adjacent pattern structures; the thickness of the second region is smaller than or equal to the average thickness of each region of the nitride layer, and/or a coarsening structure is formed on the surface of the second region, and the roughness Ra value of the surface of the second region is larger than 0.1 μm.
4. The patterned nitride single crystal substrate-based light emitting diode structure of claim 3, wherein: the thickness of the second region is 100nm-150 nm; and/or the roughness Ra value of the surface of the second region is 0.1-0.9 μm.
5. The patterned nitride single crystal substrate-based light emitting diode structure of claim 1, wherein: the filling-up layer comprises a nucleating layer, a 3D layer and a merging layer which are sequentially grown on the nitride layer, the thickness of the nucleating layer is 0-50nm, the thickness of the 3D layer is 300-800 nm, and the thickness of the merging layer is 500-1500 nm;
and/or the light-emitting epitaxial layer comprises a first semiconductor layer of a first conductivity type, a quantum well active region and a second semiconductor layer of a second conductivity type which are grown on the filling layer in sequence;
and/or the thickness of the nitride layer is 100nm-200 nm; and/or the material of the nitride layer comprises InAlN or AlN;
and/or the nitride single crystal substrate comprises a GaN single crystal substrate or an AlN single crystal substrate.
6. A method for preparing a light-emitting diode structure based on a patterned nitride single crystal substrate is characterized by comprising the following steps:
processing a plurality of regular pattern structures on the surface of the nitride single crystal substrate, wherein the pattern structures are raised or depressed relative to the surface of the nitride single crystal substrate;
forming a nitride layer on the plurality of pattern structures, enabling the nitride layer to continuously and conformally cover the plurality of pattern structures, enabling the nitride layer to be matched with the plurality of pattern structures to form a reflecting structure, and enabling the reflecting structure to at least reflect light emitted by the light-emitting epitaxial layer;
growing a filling layer with a smooth surface on the nitride layer; and
and growing a light-emitting epitaxial layer on the filling layer.
7. The method for manufacturing a light-emitting diode structure based on a patterned nitride single-crystal substrate according to claim 6, wherein: the pattern structure comprises funnel-shaped or inverted pyramid-shaped pits formed on the surface of the nitride single crystal substrate, the opening angle of each pit is 15-75 degrees, the depth of each pit is 100nm-10 mu m, the opening diameter of each pit is 10nm-1 mu m, and the distance between every two adjacent pits is 1 mu m-10 mu m;
and/or the nitride layer is formed of an Al-containing nitride, and at least one of an opening angle, an opening diameter, and a depth of the pit is decreased or increased, respectively, as Al content in the nitride layer increases or decreases;
and/or the thickness of the nitride layer is 50nm-500 nm; and/or the material of the nitride layer comprises InAlN or AlN;
and/or the nitride single crystal substrate comprises a GaN single crystal substrate or an AlN single crystal substrate.
8. The method for preparing the light-emitting diode structure based on the patterned nitride single-crystal substrate according to claim 6, comprising the following steps: and etching the surface of the nitride single crystal substrate in a dry etching and/or wet etching mode to form the pattern structure.
9. The method for preparing a light-emitting diode structure based on a patterned nitride single-crystal substrate according to claim 6, further comprising:
defining a first area and a second area in the nitride layer, wherein the first area is arranged corresponding to the pattern structures, and the second area corresponds to the area between the adjacent pattern structures; and
thinning the second region of the nitride layer until the thickness of the second region is smaller than the average thickness of each region of the nitride layer, and/or roughening the surface of the second region of the nitride layer until the roughness Ra value of the surface of the second region is larger than 0.1 μm;
and/or the thickness of the nitride layer is 100nm-200 nm.
10. The method for preparing the light-emitting diode structure based on the patterned nitride single-crystal substrate according to claim 6, comprising: growing a nucleation layer, a 3D layer and a merging layer on the nitride layer in sequence, thereby forming the filling and leveling layer;
and/or sequentially growing a first semiconductor layer of the first conduction type, a quantum well active region and a second semiconductor layer of the second conduction type on the filling layer so as to form the light-emitting epitaxial layer.
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| CN115036402A (en) * | 2022-08-12 | 2022-09-09 | 江苏第三代半导体研究院有限公司 | Induced enhanced Micro-LED homoepitaxy structure and preparation method thereof |
| CN117153974A (en) * | 2023-10-26 | 2023-12-01 | 江西兆驰半导体有限公司 | LED epitaxial wafer, preparation method thereof and LED |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN115036402A (en) * | 2022-08-12 | 2022-09-09 | 江苏第三代半导体研究院有限公司 | Induced enhanced Micro-LED homoepitaxy structure and preparation method thereof |
| CN117153974A (en) * | 2023-10-26 | 2023-12-01 | 江西兆驰半导体有限公司 | LED epitaxial wafer, preparation method thereof and LED |
| CN117153974B (en) * | 2023-10-26 | 2024-02-20 | 江西兆驰半导体有限公司 | LED epitaxial wafer, preparation method thereof and LED |
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