CN-121985644-A - Epitaxial structure, LED chip and manufacturing method thereof

CN121985644ACN 121985644 ACN121985644 ACN 121985644ACN-121985644-A

Abstract

An epitaxial structure comprises N stacked light emitting units and tunneling junctions located between two adjacent light emitting units, wherein N is more than or equal to 2, N is a positive integer, each light emitting unit comprises a first type waveguide layer, an active layer and a second type waveguide layer, each tunneling junction comprises a first type material layer and a second type material layer which are stacked, the forbidden band widths of the first type doped layer and the second type doped layer of the tunneling junction along the light emitting direction are unchanged or gradually increased, the epitaxial structure further comprises a plurality of first type reflecting layers, each first type reflecting layer is stacked on the surface of each tunneling junction facing the first type waveguide layer, or each first type reflecting layer is stacked on the surface of each first type waveguide layer facing away from the active layer. The epitaxial structure is combined with a plurality of light emitting units through the tunneling junction to form a multi-junction structure, so that the working voltage is effectively improved. And the occupied area is small, and the epitaxial area loss is reduced. Through the arrangement of the forbidden band width of the tunneling junction, light absorption from the top of the epitaxial structure along the light emitting direction is reduced, and higher light emitting efficiency is ensured.

Inventors

HAN XIAOYA
LIN ZHIWEI
Yan Yufa
CHEN RUIMIN
Xin Tianjiao
Wu Daiqiong
PENG XIANCHUN
GAO PENG

Assignees

江西乾照半导体科技有限公司

Dates

Publication Date: 20260505
Application Date: 20260303

Claims (10)

1. An epitaxial structure, comprising: n light-emitting units and tunneling junctions between two adjacent light-emitting units are sequentially stacked, wherein N is more than or equal to 2, and N is a positive integer; the light emitting unit comprises a first type waveguide layer, an active layer and a second type waveguide layer which are sequentially stacked; each tunneling junction comprises a first material layer and a second material layer which are stacked; The forbidden band width of the first type doped layer of the tunneling junction is unchanged or gradually increased along the light emergent direction of the epitaxial structure; the forbidden band width of the second type doped layer of the tunneling junction is unchanged or gradually increased along the light emergent direction of the epitaxial structure; The multi-layer structure further comprises a plurality of first-type reflecting layers, wherein the first-type reflecting layers are laminated on the surface of each tunneling junction, which faces the first-type waveguide layer, or the first-type reflecting layers are laminated on the surface of each first-type waveguide layer, which faces away from the active layer.
2. An epitaxial structure according to claim 1, wherein the doping concentration of the first type doped layer of the tunnel junction is constant or gradually decreases in the light exiting direction of the epitaxial structure; The doping concentration of the second type doping layer of the tunneling junction is unchanged or gradually reduced along the light emergent direction of the epitaxial structure.
3. An epitaxial structure according to claim 1 wherein said first type reflective layer is a DBR reflective layer; the logarithm of the first type reflecting layer gradually decreases along the light emitting direction of the epitaxial structure, and the logarithmic value range of the first type reflecting layer is 2-60, including the endpoint value.
4. An epitaxial structure according to claim 1, wherein the logarithm of said active layer decreases gradually along the light exit direction of the epitaxial structure; the logarithmic value range of the active layer is 2-20, including the end point value.
5. An epitaxial structure according to claim 1, wherein said first type reflective layer has a growth temperature higher than that of said first type waveguide layer, active layer and second type waveguide layer in said light emitting unit; the growth temperature of the first type waveguide layer, the active layer and the second type waveguide layer is higher than that of the tunneling junction; along the growth direction of the epitaxial structure, the growth temperature of the first type reflecting layer of the j-th light emitting unit is higher than that of the first type reflecting layer of the j+1-th light emitting unit; along the growth direction of the epitaxial structure, the growth temperature of the first type waveguide layer of the j-th light emitting unit is higher than that of the first type waveguide layer of the j+1th light emitting unit; Along the growth direction of the epitaxial structure, the growth temperature of the active layer of the jth light emitting unit is higher than that of the active layer of the jth+1th light emitting unit; Along the growth direction of the epitaxial structure, the growth temperature of the second type waveguide layer of the jth light-emitting unit is higher than that of the second type waveguide layer of the j+1th light-emitting unit, wherein j is more than or equal to 2 and less than or equal to N-1; along the growth direction of the epitaxial structure, the growth temperature of the ith tunneling junction is higher than that of the (i+1) th tunneling junction, wherein i < N-1 is more than or equal to 1.
6. An epitaxial structure according to claim 5, wherein the growth temperature of said first type reflective layer is 10 ℃ to 150 ℃ higher than the growth temperature of said first type waveguide layer, active layer and second type waveguide layer in said light emitting cell in contact therewith, including end point values; the growth temperature of the first type waveguide layer, the active layer and the second type waveguide layer in the light emitting unit is 40-150 ℃ higher than that of the tunneling junction on the second type waveguide layer of the light emitting unit, wherein the growth temperature comprises end point values; Along the growth direction of the epitaxial structure, the growth temperature of the first type reflecting layer of the j-th light-emitting unit is 0-30 ℃ higher than that of the first type reflecting layer of the j+1th light-emitting unit, wherein the growth temperature is higher than that of the first type reflecting layer of the j-th light-emitting unit by the right endpoint value; along the growth direction of the epitaxial structure, the growth temperature of the first type waveguide layer of the j-th light-emitting unit is 0-30 ℃ higher than that of the first type waveguide layer of the j+1th light-emitting unit, wherein the growth temperature is higher than that of the first type waveguide layer of the j-th light-emitting unit by the right endpoint value; Along the growth direction of the epitaxial structure, the growth temperature of the active layer of the jth light emitting unit is 0-30 ℃ higher than that of the active layer of the (j+1) th light emitting unit, including a right endpoint value; Along the growth direction of the epitaxial structure, the growth temperature of the second type waveguide layer of the jth light-emitting unit is 0-30 ℃ higher than that of the second type waveguide layer of the j+1th light-emitting unit, wherein j is more than or equal to 2 and less than or equal to N-1; along the growth direction of the epitaxial structure, the growth temperature of the ith tunneling junction is 0-30 ℃ higher than that of the (i+1) th tunneling junction, wherein i is more than or equal to 1 and less than N-1.
7. An LED chip is characterized by comprising a substrate, at least two epitaxial structures, a transparent conductive layer, a first electrode and a second electrode; the epitaxial structures are the epitaxial structures according to any one of claims 1-6, and the first type reflecting layers of the epitaxial structures are laminated on the surface of each first type waveguide layer, which faces away from the active layer; The transparent conducting layer is positioned between two adjacent epitaxial structures and connects the two adjacent epitaxial structures in series; the first electrode is arranged on one side of the substrate, which is away from the epitaxial lamination, and is electrically connected with the first type waveguide layer; The second electrode is arranged on one side, away from the substrate, of the epitaxial structure farthest from the substrate and is electrically connected with the second waveguide layer.
8. An LED chip is characterized by comprising a substrate, a first epitaxial structure, a second epitaxial structure, a bonding layer, a metal reflector, a first electrode and a second electrode; The first epitaxial structure is an epitaxial structure according to any one of claims 1-6, and the first type reflecting layers of the epitaxial structure are laminated on the surface of each first type waveguide layer, which faces away from the active layer; The second epitaxial structure is the epitaxial structure of any one of claims 1-6, and the first reflective layer is laminated on the surface of each tunneling junction facing the first waveguide layer; the first epitaxial structure is positioned on one side surface of the substrate; the second epitaxial structure is connected with one side of the substrate, which is away from the first epitaxial structure, through a bonding layer in a bonding way and is connected with the first epitaxial structure in series; The metal mirror is located between the bonding layer and the second epitaxial structure; the first electrode is arranged on one side of the second epitaxial structure, which is away from the substrate, and is electrically connected with the first waveguide layer; the second electrode is arranged on the surface of the first epitaxial structure, which is away from the substrate, and is electrically connected with the second waveguide layer.
9. The manufacturing method of the LED chip is characterized by comprising the following steps of: Providing a substrate; Growing an epitaxial structure on one side surface of the substrate to form an epitaxial wafer, wherein the epitaxial structure comprises N light-emitting units and tunneling junctions, wherein the N light-emitting units are sequentially stacked along the direction deviating from the substrate, the tunneling junctions are positioned between two adjacent light-emitting units, N is more than or equal to 2, and N is a positive integer; The light emitting unit comprises a first type waveguide layer, an active layer and a second type waveguide layer which are sequentially grown along the direction deviating from the substrate; The tunneling junction comprises a first material layer and a second material layer which are stacked; The forbidden band width of the first type doped layer of the tunneling junction is unchanged or gradually increased along the light emergent direction of the epitaxial structure; the forbidden band width of the second type doped layer of the tunneling junction is unchanged or gradually increased along the light emergent direction of the epitaxial structure; The method further comprises the steps of growing a plurality of first type reflecting layers, growing the first type reflecting layers before growing each first type waveguide layer, and then growing a first type waveguide layer on the first type reflecting layers; the growth temperature of the first type reflecting layer is higher than the growth temperature of the first type waveguide layer, the active layer and the second type waveguide layer in the light emitting unit, and the growth temperature of the first type waveguide layer, the active layer and the second type waveguide layer is higher than the growth temperature of the tunneling junction; along the growth direction of the epitaxial structure, the growth temperature of the first type reflecting layer of the j-th light emitting unit is higher than that of the first type reflecting layer of the j+1-th light emitting unit; along the growth direction of the epitaxial structure, the growth temperature of the first type waveguide layer of the j-th light emitting unit is higher than that of the first type waveguide layer of the j+1th light emitting unit; Along the growth direction of the epitaxial structure, the growth temperature of the active layer of the jth light emitting unit is higher than that of the active layer of the jth+1th light emitting unit; Along the growth direction of the epitaxial structure, the growth temperature of the second type waveguide layer of the jth light-emitting unit is higher than that of the second type waveguide layer of the j+1th light-emitting unit, wherein j is more than or equal to 2 and less than or equal to N-1; Along the growth direction of the epitaxial structure, the growth temperature of the ith tunneling junction is higher than that of the (i+1) th tunneling junction, wherein i is more than or equal to 1 and less than N-1; growing a first transparent conductive bonding layer on one side of one epitaxial wafer, which is away from the substrate, wherein the first transparent conductive bonding layer is electrically connected with the second waveguide layer; bonding one side of the other epitaxial wafer, which is away from the substrate, to a transfer substrate, removing the substrate, and growing a second transparent conductive bonding layer on one side of the epitaxial structure, which is away from the transfer substrate, wherein the second transparent conductive bonding layer is electrically connected with the first waveguide layer; Bonding and connecting the first transparent conductive bonding layer and the second transparent conductive bonding layer, and removing the transfer substrate; And manufacturing a first electrode and a second electrode on the epitaxial wafer which are connected in a bonding way, wherein the first electrode is arranged on one side of the substrate, which is away from the epitaxial structure, and is electrically connected with the first type waveguide layer, and the second electrode is arranged on one side of the epitaxial structure, which is away from the substrate, and is electrically connected with the second type waveguide layer.
10. The manufacturing method of the LED chip is characterized by comprising the following steps of: Providing a substrate; Growing an epitaxial structure on one side surface of the substrate to form an epitaxial wafer, wherein the epitaxial structure comprises N light-emitting units and tunneling junctions, wherein the N light-emitting units are sequentially stacked along the direction deviating from the substrate, the tunneling junctions are positioned between two adjacent light-emitting units, N is more than or equal to 2, and N is a positive integer; the light emitting unit comprises a first type waveguide layer, an active layer and a second type waveguide layer which are sequentially grown along the direction deviating from the substrate; the tunneling junction comprises a first material layer and a second material layer which are overlapped; The forbidden band width of the first type doped layer of the tunneling junction is unchanged or gradually increased along the light emergent direction of the epitaxial structure; the forbidden band width of the second type doped layer of the tunneling junction is unchanged or gradually increased along the light emergent direction of the epitaxial structure; The method comprises the steps of forming a first type waveguide layer on a substrate, forming a first type waveguide layer on the substrate, forming a plurality of first type reflecting layers on the substrate, and forming a first epitaxial wafer by growing the first type reflecting layers before growing each first type waveguide layer and then growing the first type waveguide layer on the first type reflecting layers, or growing the first type reflecting layers on each tunneling junction after growing each tunneling junction; Manufacturing a metal reflector on one side of the second epitaxial wafer, which is away from the substrate; the metal reflector of the second epitaxial wafer is bonded and connected with one side of the first epitaxial wafer substrate, which is away from the epitaxial structure, through a bonding layer, and the substrate of the second epitaxial wafer is removed; And manufacturing a first electrode and a second electrode on the first epitaxial wafer and the second epitaxial wafer which are subjected to bonding connection, wherein the first electrode is arranged on one side of the second epitaxial wafer, which is away from the first epitaxial wafer, and is electrically connected with the first type waveguide layer, and the second electrode is arranged on one side of the first epitaxial wafer, which is away from the second epitaxial wafer, and is electrically connected with the second type waveguide layer.

Description

Epitaxial structure, LED chip and manufacturing method thereof Technical Field The invention relates to the technical field of light emitting diodes, in particular to an epitaxial structure, an LED chip and a manufacturing method thereof. Background Light Emitting Diodes (LEDs) are widely used in the fields of lighting, display, communication, etc. due to their low power consumption, small size, and high reliability. With the rapid development of industry, the demand for light emitting diode power is higher and higher, the cost is lower and lower, and the trend of manufacturing high-power and low-cost light emitting diodes is growing. One important technical branch is the high voltage LED. The high-voltage LED is a high-power LED, and a LED manufacturer adopts a series-connected low-power LED to integrate a high-power LED chip. At present, the traditional chip serial connection technology adopts a chip lead technology to enable a P electrode on the top of one LED and an N electrode of another LED luminous unit to be connected with each other by adopting a plurality of LED chips on a horizontal plane, and the P electrode and the N electrode are sequentially connected for a plurality of times to form a high-voltage chip. The traditional high-voltage chip structure is adopted, on one hand, open circuits are easy to generate in the process due to the step difference of N and P connection, the failure rate is high, on the other hand, the horizontal connection technology is adopted, the area of the high-voltage LEDs is large due to the fact that the number of LEDs used is large, on the other hand, the number of grooves needed for insulation isolation is large due to the fact that the number of the LEDs is large, and the electrode area which is required to be lost is large due to the fact that the P and N electrodes of different light emitting units are connected, and therefore the loss of the epitaxial area is large as a whole. Disclosure of Invention In view of the above, the invention provides an epitaxial structure, an LED chip and a method for manufacturing the same, so as to solve the problems of large occupied area and large epitaxial area loss of the LED chip caused by the conventional horizontal serial structure. In order to achieve the above purpose, the technical scheme adopted by the invention is as follows: An epitaxial structure comprises N light emitting units and tunneling junctions, wherein the N light emitting units and the tunneling junctions are arranged between two adjacent light emitting units in a sequentially laminated mode, N is more than or equal to 2, and N is a positive integer; the light emitting unit comprises a first type waveguide layer, an active layer and a second type waveguide layer which are sequentially stacked; each tunneling junction comprises a first material layer and a second material layer which are stacked; The forbidden band width of the first type doped layer of the tunneling junction is unchanged or gradually increased along the light emergent direction of the epitaxial structure; the forbidden band width of the second type doped layer of the tunneling junction is unchanged or gradually increased along the light emergent direction of the epitaxial structure; The multi-layer structure further comprises a plurality of first-type reflecting layers, wherein the first-type reflecting layers are laminated on the surface of each tunneling junction, which faces the first-type waveguide layer, or the first-type reflecting layers are laminated on the surface of each first-type waveguide layer, which faces away from the active layer. Further, the doping concentration of the first type doped layer of the tunneling junction is unchanged or gradually reduced along the light emergent direction of the epitaxial structure; The doping concentration of the second type doping layer of the tunneling junction is unchanged or gradually reduced along the light emergent direction of the epitaxial structure. Further, the first reflective layer is a DBR reflective layer; the logarithm of the first type reflecting layer gradually decreases along the light emitting direction of the epitaxial structure, and the logarithmic value range of the first type reflecting layer is 2-60, including the endpoint value. Further, along the light emergent direction of the epitaxial structure, the logarithm of the active layer gradually decreases; the logarithmic value range of the active layer is 2-20, including the end point value. Further, the growth temperature of the first type reflecting layer is higher than the growth temperature of the first type waveguide layer, the active layer and the second type waveguide layer in the light emitting unit, and the growth temperature of the first type waveguide layer, the active layer and the second type waveguide layer is higher than the growth temperature of the tunneling junction; along the growth direction of the epitaxial structure, the growth temperature of the f