CN109638114B - Light emitting diode epitaxial wafer and preparation method thereof - Google Patents

Abstract

The invention discloses a light-emitting diode epitaxial wafer and a preparation method thereof, belonging to the field of light-emitting diode manufacturing. A low-temperature N-type GaN layer and a superlattice structure are arranged between the N-type GaN layer and the active layer in sequence. The quality of the superlattice structure grown on the GaN layer can avoid excessive defects in the superlattice structure and affect the subsequent growth of the active layer. The sublayer and the GaN sublayer can play the role of releasing the stress in the epitaxial layer, improve the overall crystal quality of the epitaxial layer, and due to the lattice between the aluminum gallium nitride sublayer, the indium gallium nitride sublayer and the GaN sublayer. The difference between the constants is large, so the interface between the three can block the dislocations, prevent the dislocations from moving to the active layer behind the superlattice structure, and ensure the crystal quality of the active layer.

Description

A kind of light-emitting diode epitaxial wafer and preparation method thereof

technical field

The invention relates to the field of light-emitting diode manufacturing, in particular to a light-emitting diode epitaxial wafer and a preparation method thereof.

Background technique

Light-emitting diodes are semiconductor diodes that can convert electrical energy into light energy. They have the advantages of small size, long life and low power consumption. They are currently widely used in car signal lights, traffic lights, display screens and lighting equipment. An epitaxial wafer is the basic structure for making light-emitting diodes. The structure of the epitaxial wafer includes a substrate and an epitaxial layer on the substrate. The epitaxial layer includes an N-type GaN layer, an active layer and a P-type GaN layer grown on the substrate in sequence.

However, in this structure, due to the large lattice mismatch between the substrate and the epitaxial layer, more defects will be generated when the epitaxial layer grows on the substrate, which affects the quality of the active layer in the epitaxial layer. The poor quality of the layer affects the recombination efficiency of electrons and holes in the active layer, which in turn leads to a low luminous efficiency of the light-emitting diode.

SUMMARY OF THE INVENTION

The embodiments of the present invention provide a light-emitting diode epitaxial wafer and a preparation method thereof, which can improve the light-emitting efficiency of the light-emitting diode. The technical solution is as follows:

An embodiment of the present invention provides a light-emitting diode epitaxial wafer, the epitaxial wafer includes a substrate and an N-type GaN layer, a low-temperature N-type GaN layer, a superlattice structure, an active layer, and an N-type GaN layer sequentially stacked on the substrate. P-type GaN layer,

The superlattice structure includes AlGaN sublayers, InGaN sublayers and GaN sublayers stacked alternately, wherein the GaN sublayers are doped with Si elements.

Optionally, the aluminum gallium nitride sublayer is an AlXGa1 _{- XN} layer, and the indium gallium nitride sublayer is an _{InZGa1 -} ZN layer, wherein 0<X<1, 0.1<Z<0.5 .

Optionally, 0.1<X<0.4, 0.1<Z<0.3.

Optionally, the thickness of the aluminum gallium nitride sub-layer, the thickness of the indium gallium nitride sub-layer, and the thickness of the GaN sub-layer are all 5-15 nm.

Optionally, the number of layers of the aluminum gallium nitride sub-layer, the number of layers of the indium gallium nitride sub-layer, and the number of layers of the GaN sub-layer are all 5-20.

Optionally, the doping concentration of Si element in the GaN sublayer is 1×10 ¹⁷ to 1×10 ¹⁸ cm ⁻³ .

Optionally, the thickness of the low temperature N-type GaN layer is 30-80 nm.

The embodiment of the present invention provides a preparation method of a light-emitting diode epitaxial wafer, and the preparation method includes:

providing a substrate;

growing an N-type GaN layer on the substrate;

growing a low temperature N-type GaN layer on the N-type GaN layer;

growing a superlattice structure on the low temperature N-type GaN layer;

growing an active layer on the superlattice structure;

growing a P-type GaN layer on the active layer,

Wherein, the superlattice structure includes AlGaN sub-layers, InGaN sub-layers and GaN sub-layers stacked alternately, wherein the GaN sub-layers are doped with Si element.

Optionally, the growth temperature of the superlattice structure is 800-900°C.

Optionally, the growth pressure of the superlattice structure is 50-300 Torr.

The beneficial effect brought by the technical solutions provided by the embodiments of the present invention is that a low-temperature N-type GaN layer and an alternately stacked AlGaN sub-layer and an InGaN sub-layer are sequentially added between the N-type GaN layer and the active layer. And the superlattice structure of the GaN sub-layer, the setting of the low-temperature N-type GaN layer can realize a good transition between the superlattice structure and the N-type GaN layer, and ensure the quality of the superlattice structure grown on the N-type GaN layer. Avoid excessive defects in the superlattice structure and affect the active layer of subsequent growth, and the alternately stacked AlGaN sublayers, InGaN sublayers and GaN sublayers in the superlattice structure can play a role in the release of the epitaxial layer. The effect of stress on the epitaxial layer improves the overall crystal quality of the epitaxial layer, and because the lattice constants between the AlGaN sublayer, the InGaN sublayer and the GaN sublayer are quite different, the interface between the three can be Blocking the dislocations prevents the dislocations from moving to the active layer behind the superlattice structure, thereby ensuring the crystal quality of the active layer, thereby improving the luminous efficiency of the light emitting diode.

Description of drawings

In order to illustrate the technical solutions in the embodiments of the present invention more clearly, the following briefly introduces the accompanying drawings used in the description of the embodiments. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can also be obtained from these drawings without creative effort.

1 is a schematic structural diagram of a light-emitting diode epitaxial wafer provided by an embodiment of the present invention;

2 is a schematic structural diagram of another light-emitting diode epitaxial wafer provided by an embodiment of the present invention;

3 is a flowchart of a method for preparing a light-emitting diode epitaxial wafer provided by an embodiment of the present invention;

FIG. 4 is a flowchart of another method for fabricating a light-emitting diode epitaxial wafer provided by an embodiment of the present invention.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

FIG. 1 is a schematic structural diagram of a light emitting diode epitaxial wafer provided by an embodiment of the present invention. As shown in FIG. 1 , the epitaxial wafer includes a substrate 1 and an N-type GaN layer 2 , a low-temperature N-type GaN layer 3 , a superlattice structure 4 , an active layer 5 and a P-type GaN layer sequentially stacked on the substrate 1 . 6.

The superlattice structure 4 includes alternately stacked AlGaN sublayers 41 , InGaN sublayers 42 and GaN sublayers 43 , wherein the GaN sublayer 43 is doped with Si element.

Between the N-type GaN layer 2 and the active layer 5 , a low-temperature N-type GaN layer 3 and a superlattice structure including alternately stacked AlGaN sublayers 41 , InGaN sublayers 42 and GaN sublayers 43 are sequentially added. 4. The setting of the low-temperature N-type GaN layer 3 can make a good transition between the superlattice structure 4 and the N-type GaN layer 2, ensure the quality of the superlattice structure 4 grown on the N-type GaN layer 3, and avoid supercrystalline Excessive defects in the lattice structure 4 affect the active layer 5 grown subsequently, and the AlGaN sublayers 41 , the InGaN sublayers 42 and the GaN sublayers 43 alternately stacked in the superlattice structure 4 can release The effect of stress in the epitaxial layer improves the overall crystal quality of the epitaxial layer, and because the lattice constants of the AlGaN sublayer 41, the InGaN sublayer 42 and the GaN sublayer 43 are quite different, the three The interface between them can block the dislocations, prevent the dislocations from moving to the active layer 5 behind the superlattice structure 4 , and ensure the crystal quality of the active layer 5 .

And since the potential barrier of the indium gallium nitride sub-layer 42 is lower than that of the GaN sub-layer 43, and the potential barrier of the GaN sub-layer 43 is lower than that of the aluminum gallium nitride sub-layer 41, electrons can be accumulated at the indium gallium nitride sub-layer 42, and cooperate with each other. The aluminum gallium nitride sub-layer 41 with a higher potential barrier blocks electrons, so that the electrons can be well expanded before entering the active layer 5. At the same time, the GaN sub-layer 43 doped with Si element can be used as a source of electrons to ensure the current At the same time of expansion, increasing the number of electrons entering the active layer 5 can improve the luminous efficiency of the light emitting diode and the luminous uniformity of the light emitting diode.

FIG. 2 is a schematic structural diagram of another light-emitting diode epitaxial wafer provided by an embodiment of the present invention. As shown in FIG. 2 , the epitaxial wafer may include a substrate 1 and a buffer layer 7 and N-type GaN sequentially stacked on the substrate 1 . Layer 2 , low temperature N-type GaN layer 3 , superlattice structure 4 , active layer 5 , low temperature P-type GaN layer 8 , electron blocking layer 9 , P-type GaN layer 6 and P-type contact layer 10 .

Exemplarily, the buffer layer 7 may include an AlN layer 71 and an undoped GaN layer 72 stacked in sequence, and the arrangement of the AlN layer 71 and the undoped GaN layer 72 can reduce the lattice between the substrate 1 and the entire epitaxial layer. The influence of mismatch is beneficial to improve the quality of the epitaxial wafer of the light emitting diode, thereby improving the luminous efficiency of the light emitting diode.

Wherein, the thickness of the AlN buffer layer 71 may be 15-40 nm. The thickness of the undoped GaN layer 72 may be 1˜5 μm.

Optionally, the doping element in the N-type GaN layer 2 may be Si. The thickness of the N-type GaN layer 5 may be 1˜5 μm. Wherein, the doping concentration of Si element can be 1×10 ¹⁸ to 1×10 ¹⁹ cm ^-3 , and the quality of the N-type GaN layer 2 obtained under this condition is good, and the quality of the epitaxial wafer of the light-emitting diode can be guaranteed.

Exemplarily, the thickness of the low temperature N-type GaN layer 3 may be 30˜80 nm. When the thickness of the low-temperature N-type GaN layer is within this range, the quality of the epitaxial thin film grown on the low-temperature N-type GaN layer can be guaranteed, and the superlattice structure grown on the low-temperature N-type GaN layer has a better stress release effect. it is good.

Optionally, the aluminum gallium nitride sublayer 41 in the superlattice structure 4 is an AlXGa1 _{- XN} layer, and the indium gallium nitride sublayer 42 is an _{InZGa1 -ZN} layer, where 0<X<1, 0.1<Z<0.5. X and Z in the Al _X Ga _1-X N layer and the In _Z Ga _1-Z N layer are respectively in the above ranges, which can ensure the quality of the superlattice structure and at the same time ensure that the superlattice structure effectively plays the role of current expansion, improving the Luminous efficiency of light-emitting diodes.

Further, 0.1<X<0.4, and 0.1<Z<0.3. Under this condition, the luminous efficiency of the light-emitting diode can be greatly improved.

Preferably, when x is 0.3 and z is 0.25, the luminous efficiency of the light-emitting diode can be effectively improved.

Optionally, the thickness of the aluminum gallium nitride sub-layer 41, the thickness of the indium gallium nitride sub-layer 42, and the thickness of the GaN sub-layer 43 are all 5-15 nm. When the thickness of the AlGaN sub-layer 41 , the thickness of the InGaN sub-layer 42 and the thickness of the GaN sub-layer 43 are all within the above ranges, the superlattice structure greatly improves the luminous efficiency of the light emitting diode.

Exemplarily, the number of layers of the aluminum gallium nitride sub-layer 41 , the number of layers of the indium gallium nitride sub-layer 42 , and the number of layers of the GaN sub-layer 43 are all 5-20. At this time, the superlattice structure greatly improves the luminous efficiency of the light emitting diode.

Optionally, the doping concentration of Si element in the GaN sublayer 43 is 1×10 ¹⁷ to 1×10 ¹⁸ cm ⁻³ . When the doping concentration of Si element in the GaN sub-layer 43 is in the above range, the luminous efficiency of the light emitting diode is better improved.

Optionally, the active layer 5 may be a multiple quantum well layer, and the active layer 5 may include an InGaN well layer 51 and a GaN barrier layer 52 stacked in sequence.

The number of layers of the InGaN well layer 51 and the GaN barrier layer 52 can both be 5-11. The light-emitting diode obtained under this condition has better luminous efficiency.

Exemplarily, the thickness of the InGaN well layer 51 may be 2-3 nm, and the thickness of the GaN barrier layer 52 may be 9-20 nm, so that the obtained light-emitting diode has better luminous efficiency.

Optionally, the thickness of the low temperature P-type GaN layer 8 may be 50˜100 nm. The low temperature P-type GaN layer is disposed between the active layer 5 and the electron blocking layer 9, which can provide holes, which is beneficial to increase the number of holes entering the active layer 5 and improve the luminous efficiency of the light emitting diode. And when the thickness of the P-type GaN layer is in the above range, the luminous efficiency of the light-emitting diode is greatly improved.

Alternatively, the electron blocking layer 9 may be a p-type _{AlyGa1 -yN} layer, where 0.1<y<0.5. The electron blocking layer is a p-type _{AlyGa1 -yN} layer, which can effectively block electrons from entering the p-type GaN layer, and can provide some holes to improve the luminous efficiency of the light-emitting diode.

The thickness of the p-type _{AlyGa1 -yN} layer may be 20-100 nm.

Exemplarily, the thickness of the P-type GaN layer 6 may be 50-100 nm.

The thickness of the P-type contact layer 10 may be 10˜50 nm.

FIG. 3 is a flowchart of a method for preparing a light-emitting diode epitaxial wafer provided by an embodiment of the present invention. As shown in FIG. 3 , the preparation method includes:

S101: Provide a substrate.

S102: growing an N-type GaN layer on the substrate.

S103 : growing a low-temperature N-type GaN layer on the N-type GaN layer.

S104: growing a superlattice structure on the low temperature N-type GaN layer.

The superlattice structure includes alternately stacked AlGaN sublayers, InGaN sublayers and GaN sublayers, wherein the GaN sublayers are doped with Si elements, and the growth temperature of the low-temperature N-type GaN layer is 800-900° C. .

S105: growing an active layer on the superlattice structure.

S106: A P-type GaN layer is grown on the active layer.

The structure of the epitaxial wafer after step S106 is performed can be seen in FIG. 1 .

Between the N-type GaN layer and the active layer, a low-temperature N-type GaN layer and a superlattice structure including alternately stacked AlGaN sub-layers, InGaN sub-layers and GaN sub-layers are sequentially added, and the low-temperature N-type GaN layer The setting can achieve a good transition between the superlattice structure and the N-type GaN layer, ensure the quality of the superlattice structure grown on the N-type GaN layer, and avoid excessive defects in the superlattice structure and affect the subsequent growth. The active layer, and the alternately stacked AlGaN sublayers, InGaN sublayers and GaN sublayers in the superlattice structure can release the stress in the epitaxial layer and improve the overall crystal quality of the epitaxial layer. The lattice constants of the AlGaN sublayer, the InGaN sublayer and the GaN sublayer are quite different, so the interface between the three can block dislocations and prevent them from moving to the superlattice structure In the subsequent active layer, the crystal quality of the active layer is guaranteed.

And because the potential barrier of the indium gallium nitride sublayer is lower than that of the GaN sublayer, and the potential barrier of the GaN sublayer is lower than that of the aluminum gallium nitride sublayer, electrons can be accumulated at the indium gallium nitride sublayer, which can be combined with the higher potential barrier. The aluminum gallium nitride sublayer blocks electrons, which can make the electrons expand well before entering the active layer. At the same time, the GaN sublayer doped with Si element can be used as a source of electrons to ensure the current expansion and increase the entry into the active layer. The number of electrons in the light-emitting diode can improve the luminous efficiency of the light-emitting diode and improve the light-emitting uniformity of the light-emitting diode.

FIG. 4 is a flowchart of another method for preparing a light-emitting diode epitaxial wafer provided by an embodiment of the present invention. As shown in FIG. 4 , the preparation method includes:

S201: Provide a substrate.

Wherein, the substrate can be a sapphire substrate.

S202: growing a buffer layer on the substrate.

Alternatively, the buffer layer may include an AlN layer and an undoped GaN layer sequentially grown on the substrate.

The AlN layer can be deposited on the surface of the substrate by the method of magnetron sputtering, and the quality of the obtained AlN layer is good.

Exemplarily, the deposition temperature of the AlN layer may be 400-800° C., the sputtering power during the deposition of the AlN layer may be 3000-5000 W, and the pressure during the deposition of the AlN layer may be 4-6 torr. The quality of the AlN layer obtained under the above conditions is good, which is beneficial to ensure the overall quality of the epitaxial wafer.

Optionally, the growth temperature of the undoped GaN layer may be 1000˜1100° C., and the growth pressure of the undoped GaN layer may be 100˜500 Torr, and the quality of the undoped GaN layer grown under these conditions is good.

The growth thickness of the undoped GaN layer may be 1˜5 μm.

S203 : growing an N-type GaN layer on the buffer layer.

Wherein, the growth thickness of the N-type GaN layer may be 1-5 μm.

The growth temperature of the N-type GaN layer may be 1000˜1200° C., and the growth pressure of the N-type GaN layer may be 100˜500 Torr.

S204 : growing a low-temperature N-type GaN layer on the N-type GaN layer.

Wherein, the growth thickness of the low-temperature N-type GaN layer may be 30-80 nm. The growth temperature of the low-temperature N-type GaN layer can be 800-900° C., and the low-temperature N-type GaN layer grown under this condition can effectively improve the overall quality of the light-emitting diode, and is conducive to ensuring the luminous efficiency of the light-emitting diode.

Wherein, when the growth thickness of the low-temperature N-type GaN layer is 50 nm, the luminous efficiency of the light-emitting diode can be better improved.

Optionally, the growth pressure of the low-temperature N-type GaN layer is 100-300 Torr, and the low-temperature N-type GaN layer grown under this condition can effectively improve the overall quality of the light-emitting diode, which is beneficial to ensure the light-emitting efficiency of the light-emitting diode.

S205 : growing a superlattice structure on the low-temperature N-type GaN layer.

The superlattice structure includes alternately stacked AlGaN sublayers, InGaN sublayers and GaN sublayers, wherein the GaN sublayers are doped with Si elements.

Among them, the growth temperature of the superlattice structure is 800-900°C. The quality of the superlattice structure grown under this condition is good, and the luminous efficiency of the light-emitting diode can be effectively improved.

Exemplarily, the growth pressure of the superlattice structure is 50-300 Torr. The quality of the superlattice structure grown under this condition is good, and the luminous efficiency of the light-emitting diode can be effectively improved.

Optionally, the growth thickness of the aluminum gallium nitride sublayer, the growth thickness of the indium gallium nitride sublayer, and the growth thickness of the GaN sublayer can all be 5-15 nm.

S206: growing an active layer on the superlattice structure.

The active layer may include an InGaN well layer and a GaN barrier layer stacked in sequence.

Exemplarily, the growth thickness of the InGaN well layer may be 2-3 nm, and the growth thickness of the GaN barrier layer may be 9-20 nm, and the obtained light-emitting diode has better luminous efficiency.

Optionally, the growth temperature of the InGaN well layer may be 720-830°C, and the growth temperature of the GaN barrier layer may be 850-960°C. Luminous efficiency.

Further, the growth pressure of the InGaN well layer and the growth pressure of the GaN barrier layer can both be 100-500 Torr, and the quality of the active layer grown under this condition is good, and the luminous efficiency of the light-emitting diode can be guaranteed.

S207 : growing a low temperature P-type GaN layer on the active layer.

Optionally, the growth thickness of the low temperature P-type GaN layer may be 50-100 nm.

The growth temperature of the low-temperature P-type GaN layer may be 600˜800° C., and the growth pressure of the low-temperature P-type GaN layer may be 200˜500 Torr. The quality of the low-temperature P-type GaN layer grown under this condition is good, which is beneficial to improve the luminous efficiency of the light-emitting diode.

S208: growing an electron blocking layer on the low temperature P-type GaN layer.

The growth thickness of the p-type _{AlyGa1 -yN} layer may be 20-100 nm.

The growth temperature of the p-type _{AlyGa1 -} yN layer may be 700˜1000° C., and the growth pressure of the p-type _{AlyGa1 -yN} layer may be 100˜500 Torr. The quality of the p-type _{AlyGa1 -yN} layer grown under this condition is good, which is beneficial to improve the luminous efficiency of the light-emitting diode.

S209: Grow a P-type GaN layer on the electron blocking layer.

Exemplarily, the growth thickness of the P-type GaN layer may be 50˜100 nm.

Optionally, the growth pressure of the P-type GaN layer may be 200-600 Torr, and the growth temperature of the P-type GaN layer may be 900-1000°C.

S210: growing a P-type contact layer on the P-type GaN layer.

Wherein, the growth thickness of the P-type contact layer may be 10-50 nm.

Exemplarily, the growth temperature of the P-type contact layer may be 850˜1000° C., and the growth pressure of the P-type contact layer may be 100˜300 torr.

The structure of the epitaxial wafer after step S210 is performed can be seen in FIG. 2 .

It should be noted that, in the embodiments of the present invention, other structures except the AlN layer are grown by MOCVD (chemical vapor deposition) method. In the growth process of the above structure, trimethyl (or triethyl) gallium is used as gallium source, high-purity _NH3 is used as nitrogen source, trimethylindium is used as indium source, trimethylaluminum is used as aluminum source, and n-type doping Silane is used for hybrid, and magnesium locene is used for p-type doping.

The above method may further include, after the growth of the above-mentioned epitaxial structure is completed, lowering the temperature in the MOCVD (chemical vapor deposition) process chamber, and performing annealing treatment on the epitaxial wafer in a nitrogen atmosphere, the annealing temperature range is 650-850 ° C, and the annealing treatment is 5 ~15 minutes, approaching room temperature, ending epitaxial growth. Annealing can further remove defects in the epitaxial wafer, which is beneficial to improve the luminous efficiency of the light emitting diode.

The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection of the present invention. within the range.

Claims (8)

1. A light-emitting diode epitaxial wafer, wherein the epitaxial wafer comprises a substrate and an N-type GaN layer, a low-temperature N-type GaN layer, a superlattice structure, an active layer and P-type GaN layer, the low-temperature N-type GaN layer is grown at a temperature of 800-900°C, The superlattice structure includes alternately stacked AlGaN sub-layers, InGaN sub-layers and GaN sub-layers, wherein the GaN sub-layer is doped with Si element, and the Al-GaN sub-layer is Al _X Ga _{1- X} N layer, the indium gallium nitride sublayer is an In _Z Ga _1-Z N layer, wherein 0.1< _X <0.4, 0.1< _Z <0.3. 2 . The epitaxial wafer according to claim 1 , wherein the thickness of the aluminum gallium nitride sublayer, the thickness of the indium gallium nitride sublayer, and the thickness of the GaN sublayer are all 5-15 nm. 3 . 3 . The epitaxial wafer according to claim 1 , wherein the number of the aluminum gallium nitride sublayers, the number of the indium gallium nitride sublayers, and the number of the GaN sublayers are all 5˜5. 4 . 20. 4 . The epitaxial wafer according to claim 1 , wherein the doping concentration of Si element in the GaN sublayer is 1×10 ¹⁷ to 1×10 ¹⁸ cm ⁻³ . 5 . 5 . The epitaxial wafer according to claim 1 , wherein the thickness of the low-temperature N-type GaN layer is 30-80 nm. 6 . 6. A preparation method of a light-emitting diode epitaxial wafer, wherein the preparation method comprises: providing a substrate; growing an N-type GaN layer on the substrate; growing a low-temperature N-type GaN layer on the N-type GaN layer, and the growth temperature of the low-temperature N-type GaN layer is 800-900° C.; growing a superlattice structure on the low temperature N-type GaN layer; growing an active layer on the superlattice structure; growing a p-type GaN layer on the active layer, The superlattice structure includes AlGaN sublayers, InGaN sublayers and GaN sublayers stacked alternately, wherein the GaN sublayer is doped with Si element, and the AlGaN sublayer is _{AlXGa A 1-X} N layer, the indium gallium nitride sublayer is an In _Z Ga _1-Z N layer, wherein 0.1< _X <0.4 and 0.1< _Z <0.3. 7 . The preparation method according to claim 6 , wherein the growth temperature of the superlattice structure is 800-900° C. 8 . 8 . The preparation method according to claim 6 , wherein the growth pressure of the superlattice structure is 50-300 Torr. 9 .

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