CN109244203B - Epitaxial wafer of light emitting diode and preparation method thereof - Google Patents

Abstract

The invention discloses an epitaxial wafer of a light emitting diode and a preparation method thereof, belonging to a light emitting diodeThe field of pole tube manufacture. In disposed between the AlN layer and the low-temperature GaN layer_xAl_1‑xWhen x of the N layer is In the range of 0.16 to 0.18, In is present_xAl_1‑xAl atoms and N atoms In the N layer structure are shared with those In the AlN layer structure, whereby In can be secured_xAl_1‑xGood connection and growth of N layer on AlN layer, In_xAl_1‑xThe quality and the surface smoothness of the N layer are good; on the other hand, In at this time_xAl_1‑xThe lattice constant of the unit cell In the N layer is closer to that of the unit cell In the low-temperature GaN layer, the lattice mismatch between the N layer and the unit cell is smaller, and In can be obtained_xAl_1‑xAnd a low-temperature GaN layer with good crystal quality is grown on the N layer. In_xAl_1‑xThe N layer relieves the original lattice mismatch between the AlN layer and the low-temperature GaN layer, the AlN layer and the low-temperature GaN layer are connected, the quality of the finally grown low-temperature GaN layer can be guaranteed, the crystal defects in the epitaxial layer can be reduced, the overall quality of the light-emitting diode can be improved, and the light-emitting efficiency of the light-emitting diode can be further improved.

Description

Epitaxial wafer of light-emitting diode and preparation method thereof

technical field

The invention relates to the field of light-emitting diode manufacturing, in particular to an epitaxial wafer of a light-emitting diode 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. The epitaxial wafer is the basic structure for making light-emitting diodes, and the structure of the epitaxial wafer includes a substrate and an epitaxial layer grown on the substrate. The structure of the epitaxial layer mainly includes: an AlN layer, a low temperature GaN layer, an undoped GaN layer, an N-type GaN layer, an active layer and a P-type GaN layer sequentially grown on the substrate.

The AlN layer, the low-temperature GaN layer and the undoped GaN layer can alleviate the lattice mismatch between the substrate and the N-type GaN layer, and reduce the lattice mismatch between the substrate and the N-type GaN layer in the epitaxial layer. defects, improve the crystal quality of the light-emitting diode, thereby improving the luminous efficiency of the light-emitting diode. However, since there is also a certain lattice mismatch between the AlN layer and the low-temperature GaN layer, the lattice mismatch between the AlN layer and the low-temperature GaN layer will also bring quality defects to the epitaxial layer, so that the luminous efficiency of the light-emitting diode cannot be obtained. greatly improved.

SUMMARY OF THE INVENTION

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

An embodiment of the present invention provides an epitaxial wafer of a light emitting diode, the epitaxial wafer includes a substrate and an AlN layer, an InxAl1 _- xN layer, a low-temperature GaN layer, an undoped layer and an AlN layer, an InxAl1- _xN layer, a low-temperature GaN layer, and an AlN layer, which are sequentially stacked on the substrate. The hetero GaN layer, the N-type GaN layer, the active layer and the P-type GaN layer, wherein 0.16≤x≤0.18.

Optionally, the thickness of the In _x Al _1-x N layer is 20-30 nm.

Optionally, the thickness of the AlN layer is 5-10 nm.

An embodiment of the present invention provides a method for preparing an epitaxial wafer of a light-emitting diode, and the preparation method includes:

providing a substrate;

growing an AlN layer on the substrate;

growing an In _x Al _1-x N layer on the AlN layer, wherein 0.16≤x≤0.18;

growing a low temperature GaN layer on the InxAl1 _{-xN layer} ;

growing an undoped GaN layer on the low temperature GaN layer;

growing an N-type GaN layer on the undoped GaN layer;

growing an active layer on the N-type GaN layer;

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

Optionally, when growing the In _x Al _1-x N layer, gaseous Al and gaseous In are introduced into the reaction chamber, and the gaseous Al introduced into the reaction chamber and the gaseous Al introduced into the reaction chamber are introduced into the reaction chamber. The ratio of gaseous In is 1:0.25～1:0.28.

Optionally, when growing the InxAl1 _{- xN} layer:

Gaseous Al of 50-100 sccm was introduced into the reaction chamber.

Optionally, when growing the InxAl1 _{- xN} layer:

Gaseous In of 100-120 sccm was introduced into the reaction chamber.

Optionally, the growth temperature of the AlN layer is 450-700°C.

Optionally, the growth temperature of the InxAl1 _{- xN} layer is 500-600°C.

Optionally, the growth pressure of the AlN layer and the growth pressure of the InxAl1 _{- xN} layer are both 30-100 Torr.

The beneficial effects brought about by the technical solutions provided in the embodiments of the present invention are: when the In _x Al _1-x N layer disposed between the AlN layer and the low-temperature GaN layer, when x is in the range of 0.16 to 0.18, on the one hand, due to the In _x In the Al _1-x N layer structure and the AlN layer structure, there are shared Al atoms and N atoms, which can ensure the good connection and growth of the In _x Al _1-x N layer on the AlN layer, and the In _x Al _1-x The quality and surface flatness of the N layer itself are better; on the other hand, the lattice constant of the unit cell in the In _x Al _1-x N layer is relatively close to the lattice constant of the unit cell in the low temperature GaN layer. The lattice mismatch between them is small, and a low-temperature GaN layer with good crystal quality can be obtained on the In _x Al _{1-x N layer} . Some lattice mismatches can not only connect the AlN layer and the low-temperature GaN layer, but also ensure the quality of the final grown low-temperature GaN layer and reduce the crystal defects in the epitaxial layer, thereby improving the overall quality of the light-emitting diode. The luminous efficiency of the light-emitting diode is further improved.

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 an epitaxial wafer of a light-emitting diode provided by an embodiment of the present invention;

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

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

FIG. 4 is a flowchart of another method for fabricating an epitaxial wafer of a light-emitting diode 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 an epitaxial wafer of a light emitting diode according to an embodiment of the present invention. As shown in FIG. 1 , the epitaxial wafer includes a substrate 1 and an AlN layer 2 , an In _x Al _1-x N layer 3 , a low-temperature GaN layer 4 , an undoped GaN layer 5 , and N layers stacked on the substrate 1 in sequence. type GaN layer 6 , active layer 7 and P-type GaN layer 8 . Among them, 0.16≤x≤0.18.

The In _x Al _1-x N layer disposed between the AlN layer and the low-temperature GaN layer, when x is in the range of 0.16 to 0.18, on the one hand, because the In _x Al _1-x N layer structure is shared with the AlN layer structure. The Al atoms and N atoms of the In x Al _{1-x N layer can ensure the good connection and growth of the In x Al 1-x N} layer on the AlN layer, and the quality and surface flatness of the In _x Al _1-x N layer itself are better; , at this time, the lattice constant of the unit cell in the In _x Al _1-x N layer is relatively close to the lattice constant of the unit cell in the low temperature GaN layer, and the lattice mismatch between the two is small, which can be obtained in In _x Al The low-temperature GaN layer with good crystal quality grown on the _1-x N layer, the In _x Al _1-x N layer alleviates the original lattice mismatch between the AlN layer and the low-temperature GaN layer, and acts to connect the AlN layer and the low-temperature GaN layer. At the same time, it can also ensure the quality of the final grown low-temperature GaN layer and reduce the effect of crystal defects in the epitaxial layer, thereby improving the overall quality of the light-emitting diode and further improving the luminous efficiency of the light-emitting diode.

FIG. 2 is a schematic structural diagram of another epitaxial wafer of a light-emitting diode provided by an embodiment of the present invention. As shown in FIG. 2 , the epitaxial wafer includes a substrate 1 and an AlN layer 2 , an In _x Al _1-x N layer 3 , a low temperature GaN layer 4 , an undoped GaN layer 5 , and an N layer 2 stacked on the substrate 1 in sequence. GaN layer 6 , stress release layer 9 , active layer 7 , electron blocking layer 10 , P-type GaN layer 8 and P-type contact layer 11 . Among them, 0.16≤x≤0.18.

Illustratively, the substrate 1 may be a sapphire substrate.

Optionally, the thickness of the AlN layer 2 is 5-10 nm. When the thickness of the AlN layer is set in the above range, the overall quality of the obtained epitaxial wafer is good, and the luminous efficiency of the light emitting diode can be improved.

Exemplarily, the thickness of the InxAl1 _{- xN} layer 3 may be 20˜30 nm. When the thickness of the In _x Al _1-x N layer is set in the above range, the overall quality of the obtained epitaxial wafer is good, and the luminous efficiency of the light emitting diode can be improved.

Wherein, x in the In _x Al _1-x N layer 3 may be 0.18. When _x in the InxAl1 _- xN layer is 0.18, the matching of lattice constants between the InxAl1 _{- xN} layer and the low temperature GaN layer is better, thereby making the luminous efficiency of the light-emitting diode better.

Optionally, the thickness of the low temperature GaN layer 4 may be 20˜30 nm. In the embodiment of the present invention, the thickness of the low-temperature GaN layer may also be 20 nm, which is not limited in the present invention.

Exemplarily, the thickness of the undoped GaN layer 5 may be 0.1˜2 μm. In the embodiment of the present invention, the thickness of the undoped GaN layer may also be 1 μm, which is not limited in the present invention.

Optionally, the doping element in the N-type GaN layer 6 may be Si, and the doping concentration of Si may be 10 ¹⁸ -10 ¹⁹ cm ^-3 .

Further, the thickness of the N-type GaN layer 6 may be 1˜5 μm. In the embodiment of the present invention, the thickness of the N-type GaN layer may also be 2 μm, which is not limited in the present invention.

Optionally, the stress release layer 9 may include alternately stacked stress release InGaN layers 91 and stress release GaN layers 92. In the embodiment provided by the present invention, the stress release InGaN layer 91 may have a thickness of 2 nm, and the stress release GaN layer 92 may have a thickness of 2 nm. The thickness can be 30nm, which can release the stress in the epitaxial wafer and improve the luminous efficiency of the light-emitting diode.

In the embodiment of the present invention, the active layer 7 may include alternately stacked InGaN well layers 71 and GaN barrier layers 72 , the thickness of the InGaN well layer 71 may be 1-3 nm, and the thickness of the GaN barrier layer 72 may be 9-20 nm . In the embodiment of the present invention, the thickness of the InGaN well layer may also be 2.5 nm, and the thickness of the GaN barrier layer 72 may also be 15 nm, which is not limited in the present invention.

The number of InGaN well layers 71 may be 8-10, and the number of GaN barrier layers 72 and InGaN well layers 71 are the same. In the embodiment of the present invention, the number of InGaN well layers 71 may be 6, which is not limited in the present invention.

Alternatively, the electron blocking layer 10 may be an AlGaN layer, and its thickness may be 80 nm.

Illustratively, the thickness of the P-type GaN layer 8 may be 0.2 μm.

Exemplarily, the thickness of the P-type contact layer 11 may be 15 nm.

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

Step S101: providing a substrate.

Step S102: growing an AlN layer on the substrate.

Step S103: growing an InxAl1 _{-xN layer} on the AlN layer, wherein 0.16≤x≤0.18.

Step S104: growing a low temperature GaN layer on the InxAl1 _{-xN layer} .

Step S105 : growing an undoped GaN layer on the low temperature GaN layer.

Step S106: growing an N-type GaN layer on the undoped GaN layer.

Step S107: growing an active layer on the N-type GaN layer.

Step S108: growing a P-type GaN layer on the active layer.

The In _x Al _1-x N layer disposed between the AlN layer and the low-temperature GaN layer, when x is in the range of 0.16 to 0.18, on the one hand, because the In _x Al _1-x N layer structure is shared with the AlN layer structure. The Al atoms and N atoms of the In x Al _{1-x N layer can ensure the good connection and growth of the In x Al 1-x N} layer on the AlN layer, and the quality and surface flatness of the In _x Al _1-x N layer itself are better; , at this time, the lattice constant of the unit cell in the In _x Al _1-x N layer is relatively close to the lattice constant of the unit cell in the low temperature GaN layer, and the lattice mismatch between the two is small, which can be obtained in In _x Al The low-temperature GaN layer with good crystal quality grown on the _1-x N layer, the In _x Al _1-x N layer alleviates the original lattice mismatch between the AlN layer and the low-temperature GaN layer, and acts to connect the AlN layer and the low-temperature GaN layer. At the same time, it can also ensure the quality of the final grown low-temperature GaN layer and reduce the effect of crystal defects in the epitaxial layer, thereby improving the overall quality of the light-emitting diode and further improving the luminous efficiency of the light-emitting diode.

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

Step S201: Provide a substrate.

Optionally, the substrate may be annealed in a hydrogen atmosphere prior to growing the AlN layer on the substrate. Part of impurities on the substrate can be removed to ensure the quality of the epitaxial layer grown on the substrate.

The temperature when the substrate is annealed in a hydrogen atmosphere may be 1050°C. Most impurities on the substrate can be removed at this temperature.

Wherein, the substrate can be a sapphire substrate.

Step S202: growing an AlN layer on the substrate.

Optionally, the growth temperature of the AlN layer is 450-700°C. The quality of the AlN layer grown under this temperature condition is good, and the quality of the epitaxial layer grown on the AlN layer can be guaranteed.

Optionally, the thickness of the AlN layer may be 5-10 nm. At this time, the growth quality of the AlN layer itself can be guaranteed, and the quality of the In _x Al _1-x N layer grown on the AlN layer can also be guaranteed.

Optionally, the growth pressure of the AlN layer may be 30-100 Torr. The quality of the AlN layer grown under this condition is good, and the quality of the epitaxial layer grown on the AlN layer can be guaranteed.

Step S203: growing an InxAl1 _{-xN layer} on the AlN layer, wherein 0.16≤x≤0.18.

Optionally, wherein, when the In _x Al _1-x N layer is grown, gaseous Al and gaseous In are introduced into the reaction chamber, and the gaseous Al introduced into the reaction chamber and the gaseous In introduced into the reaction chamber are mixed. The ratio is 1:0.25～1:0.28. Under this condition, an In _x Al _1-x N layer with better quality and less lattice mismatch with the undoped GaN layer can be grown, thereby ensuring the overall quality of the epitaxial layer and ensuring the light emitting of the light-emitting diode. efficiency.

Optionally, when growing the In _x Al _1-x N layer, gaseous Al of 50-100 sccm may be introduced into the reaction chamber. In this case, the quality of the grown InxAl1 _{- xN} layer is good, and the luminous efficiency of the light-emitting diode can be guaranteed.

Optionally, when the In _x Al _1-x N layer is grown, gaseous In of 100-120 sccm may be introduced into the reaction chamber. In this case, the quality of the grown InxAl1 _{- xN} layer is good, and the luminous efficiency of the light-emitting diode can be guaranteed.

Wherein, the growth temperature of the InxAl1 _{- xN} layer may be 500-600°C. The quality of the In _x Al _1-x N layer grown at this temperature is good, which can ensure that the In _x Al _1-x N layer can effectively alleviate the lattice mismatch between the AlN layer and the undoped GaN layer. .

Optionally, the growth pressure of the In _x Al _1-x N layer is the same as the growth pressure of the AlN layer, and both can be 30-100 Torr. The quality of the In _x Al _1-x N layer grown under this condition is good, which can ensure the quality of the epitaxial layer grown on the In _x Al _1-x N layer, and the quality of the epitaxial layer grown on the In _x Al ₁ -x N layer can be guaranteed. Using the same pressure for _-x N layers also reduces the growth time required for both.

Step S204: growing a low temperature GaN layer on the InxAl1 _{-xN layer} .

Optionally, after the growth of the low temperature GaN layer is completed, the low temperature GaN layer may be subjected to an in-situ annealing treatment for 8 minutes. The overall crystal quality of the low-temperature GaN layer is improved, thereby ensuring the quality of the epitaxial layer grown on the low-temperature GaN layer.

The temperature of the in-situ annealing treatment may be 1000-2000°C.

Step S205: growing an undoped GaN layer on the low temperature GaN layer.

Exemplarily, the growth temperature of the undoped GaN layer may be 1000˜1100° C., and the growth pressure may be 30˜100 Torr. The quality of the undoped GaN layer grown under this condition is better.

Exemplarily, the thickness of the undoped GaN layer may be 0.1˜2 μm.

Step S206: growing an N-type GaN layer on the undoped GaN layer.

Optionally, the doping element of the N-type GaN layer is Si element, and the doping concentration of Si element is 2×10 ¹⁷ cm ⁻³ .

Wherein, the growth temperature of the N-type GaN layer may be 1000˜1200° C., and the growth pressure may be 100˜300 Torr.

Step S207 : growing a stress release layer on the N-type GaN layer.

The stress release layer may include alternately stacked stress release InGaN layers and stress release GaN layers, the stress release InGaN layer may have a thickness of 2 nm, and the stress release GaN layer may have a thickness of 30 nm.

Optionally, the growth temperature of the stress-releasing InGaN layer may be 720-929° C., and the growth temperature of the stress-releasing GaN layer may be 850-959° C.

Step S208: growing an active layer on the stress release layer.

The active layer may include alternately stacked InGaN well layers and GaN barrier layers. The growth temperature of the InGaN well layer can be 720-929°C, the growth pressure of the InGaN well layer can be 100-500 Torr, the growth thickness of the InGaN well layer can be 2-3nm; the growth temperature of the GaN barrier layer can be 850-959°C, The growth pressure of the GaN barrier layer may be 100-500 Torr, and the growth thickness of the GaN barrier layer may be 9-20 nm.

Step S209: growing an electron blocking layer on the active layer.

Alternatively, the electron blocking layer may be an AlGaN layer, and its thickness may be 80 nm.

Step S210: growing a P-type GaN layer on the electron blocking layer.

In this embodiment, the growth temperature of the P-type GaN layer may be 750˜1050° C., and the growth pressure may be 100˜500 Torr.

Step S211 : growing a P-type contact layer on the P-type GaN layer.

Wherein, the thickness of the P-type contact layer may be between 5 nm and 300 nm, the growth temperature range is 850-1050° C., and the growth pressure range is 100-600 Torr.

The schematic structural diagram of the epitaxial wafer after step S210 is performed can be shown in FIG. 2 . The epitaxial wafer includes a substrate 1 and an AlN layer 2 , an In _x Al _1-x N layer 3 , an undoped layer 2 stacked on the substrate 1 in sequence, and a The hetero GaN layer 5 , the N-type GaN layer 6 , the stress release layer 9 , the active layer 7 , the electron blocking layer 10 , the P-type GaN layer 8 and the P-type contact layer 11 .

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. an epitaxial wafer of a light-emitting diode, characterized in that the epitaxial wafer comprises a substrate and an AlN layer, an In _x Al _1-x N layer, a low-temperature GaN layer, an undoped layer of AlN that are sequentially stacked on the substrate. The hetero GaN layer, the N-type GaN layer, the active layer and the P-type GaN layer, wherein 0.16≤x≤0.18, the thickness of the AlN layer is 5-10 nm, and the thickness of the In _x Al _1-x N layer is 20-30 nm, and the thickness of the low-temperature GaN layer is 20-30 nm. 2. A preparation method of an epitaxial wafer of a light-emitting diode, wherein the preparation method comprises: providing a substrate; growing an AlN layer on the substrate, the thickness of the AlN layer being 5-10 nm; growing an InxAl1 _{-xN layer} on the AlN layer, wherein 0.16≤x≤0.18, and the thickness of the InxAl1 _{- xN} layer is 20-30 nm; growing a low temperature GaN layer on the In _x Al _1-x N layer, the thickness of the low temperature GaN layer being 20-30 nm; growing an undoped GaN layer on the low temperature GaN layer; growing an N-type GaN layer on the undoped GaN layer; growing an active layer on the N-type GaN layer; A P-type GaN layer is grown on the active layer. 3. The preparation method according to claim 2, wherein when growing the In _x Al _1-x N layer, gaseous Al and gaseous In are fed into the reaction chamber, and gaseous In is fed into the reaction chamber The ratio of the gaseous Al to the gaseous In introduced into the reaction chamber is 1:0.25-1:0.28. 4. preparation method according to claim 3, is characterized in that, when growing described In _x Al _1-x N layer: Gaseous Al of 50-100 sccm was introduced into the reaction chamber. 5. preparation method according to claim 4 is characterized in that, when growing described In _x Al _1-x N layer: Gaseous In of 100-120 sccm was introduced into the reaction chamber. 6 . The preparation method according to claim 2 , wherein the growth temperature of the AlN layer is 450-700° C. 7 . 7 . The preparation method according to claim 2 , wherein the growth temperature of the InxAl1-xN layer is 500˜600° C. 8 . 8 . The preparation method according to claim 2 , wherein the growth pressure of the AlN layer and the growth pressure of the In _x Al _1-x N layer are both 30 to 100 Torr. 9 .

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