CN102447027A - Vertical structure type light-emitting diode with high light extraction window - Google Patents

Abstract

The invention relates to the field of semiconductor optoelectronic devices, in particular to a vertical structure type light-emitting diode with a high light extraction window. The invention comprises an electrode, a window layer structure for high light extraction, a contact layer, a limiting layer and a multi-quantum well active region; the high-light extraction window layer structure comprises an electrode, a high-light extraction window layer structure, a limiting layer, a multi-quantum well active region, a limiting layer and a contact layer, wherein the electrode is vertically connected from top to bottom in sequence; the polarities of the electrodes on the two sides of the multi-quantum well active region are different; the electrode on one side of the multiple quantum well active region, the window layer structure for high light extraction and the limiting layer have the same polarity, and the limiting layer, the contact layer and the electrode on the other side of the multiple quantum well active region have the same polarity. The GaN-based light emitting diode has the characteristics of low working voltage and high light extraction efficiency simultaneously by adopting the vertical structure and the thick semiconductor window layer.

Description

A Vertically Structured Light-Emitting Diode with a High Light Extraction Window

field of invention

The invention relates to the field of semiconductor optoelectronic devices, in particular to a vertical structure GaN-based light emitting diode with a low contact resistance and a high light extraction window layer.

Background technique

GaN and ZnO play an irreplaceable role in energy-saving, high-efficiency, and long-life light source LEDs due to their excellent performance. GaN-based LEDs with conventional structures have made great progress, but there are still some key issues that have not been resolved. Question 1: As shown in Figure 1, the two PN electrodes are on the same side, and the current accumulation effect is obvious. It will be found that the current is concentrated under the electrodes. Due to the blocking of the electrodes themselves, the light emitted under the electrodes is absorbed by the electrodes themselves or It is reflected by the electrodes, which seriously reduces the light extraction efficiency and also leads to the problem of higher voltage. Problem 2: As shown in Figure 2, due to the thin window layer of traditional LEDs, most of the light generated in the active area is emitted through the upper surface. Due to the thin window layer, there is very little light emitted from the side, resulting in low light extraction efficiency.

In order to solve the above two problems, various solutions have been proposed at home and abroad. For example, in view of the problem of the current concentration effect, someone proposes a method of adding a current blocking layer under the P electrode in FIG. 1 . As shown in Figure 3, the added current blocking layer can make no current flow under the electrode, no photons will be generated in its active area, and there is no phenomenon that the electrode blocks photons, and it also expands the current. However, there is still a large current accumulation in the current in the N region, which increases the operating voltage of the light emitting diode. For the research on improving the side light extraction, some people propose to increase the side light extraction rate by increasing the thickness of the window layer or changing the geometric shape of the window layer, so as to obtain higher light extraction efficiency. However, due to the increase of the window layer, the series resistance also increases, thereby increasing the working voltage of the light-emitting diode. Therefore, these studies have only effectively solved a single problem, and are subject to certain limitations in application.

Contents of the invention

The object of the present invention is to invent a vertical GaN-based light-emitting diode with low contact resistance and high light extraction window layer, so as to solve the above two problems simultaneously, so that the GaN-based light-emitting diode has both low operating voltage and Characterized by high light extraction efficiency. The technical scheme that the present invention adopts is as follows:

A vertical light-emitting diode with a high-light extraction window includes an electrode, a window layer structure for high-light extraction, a contact layer, a confinement layer, and a multi-quantum well active region; an electrode, a window layer structure for high-light extraction, a confinement layer, and multiple quantum wells The active region, confinement layer, contact layer, and electrodes are connected vertically from top to bottom; the electrodes on both sides of the multi-quantum well active region have different polarities; the electrodes on one side of the multi-quantum well active region have a window layer structure for high light extraction and the confinement layer have the same polarity, and the confinement layer on the other side of the multi-quantum well active region, the contact layer and the electrode have the same polarity.

The window layer structure for highlight extraction is composed of a semiconductor window layer and a contact layer vertically connected; the electrode in the light-emitting diode is vertically connected with the semiconductor window layer in the window structure for highlight extraction, and the window for highlight extraction The contact layer in the structure is vertically connected to the confinement layer in the LED.

The material used for the semiconductor window layer is a transparent and conductive material.

The thickness of the semiconductor window layer is greater than or equal to

The above-mentioned semiconductor window layer can be N-ZnO, N-GaP, etc., and the semiconductor window layer can be in the shape of an inverted trapezoid or a column shape, etc.; the contact layer can be an InGaN semiconductor layer, a superlattice structure SPS, or a GaN semiconductor layer, etc. The vertical structure type GaN-based light-emitting diode can be formed after peeling off the sapphire substrate, or can be formed by epitaxial growth on the conductive substrate.

As shown in FIG. 4 , since the present invention adopts a vertical structure, the voltage will be significantly reduced after the current is expanded. In addition, a thick semiconductor window layer is used in the present invention, so when emitting light, the light output from the side can be enhanced, thereby improving the light extraction efficiency.

Description of drawings:

Figure 1 is a schematic diagram of the current concentration effect of a conventional GaN-based light-emitting diode

11N electrode

12P electrode

13 thin window layers

14P type GaN semiconductor layer

15 quantum well active area

16N-type GaN semiconductor layer

17 sapphire substrate

The arrows in the figure indicate the direction of the current, and the degree of density indicates the current density.

Accompanying drawing 2 is a schematic diagram of conventional thin window layer GaN-based light-emitting diodes emitting light

21 thin window layers

22P type GaN semiconductor layer

23 quantum well active area

24N type GaN semiconductor layer

25 sapphire substrate

The cones in the diagram represent the regions where light exits from the upper surface.

Accompanying drawing 3 is a schematic diagram of a conventional GaN-based light-emitting diode with an added current blocking layer

31P electrode

32N electrode

33 thin window layers

34 current limiting layer

35P type GaN semiconductor layer

36 quantum well active area

37N type GaN semiconductor layer

38 sapphire substrate

Accompanying drawing 4 is the schematic diagram of the vertical structure light-emitting diode of embodiment 1

41N electrode

42 semiconductor window layer

43N type contact layer

44N type GaN semiconductor confinement layer

45 multiple quantum well active region

46P type GaN semiconductor confinement layer

47P type GaN contact layer

48P electrode

The arrow indicates the direction of the light

The schematic diagram of the vertical structure light-emitting diode of the second embodiment of accompanying drawing 5

51P electrode

52 semiconductor window layer

53P type contact layer

54P type GaN semiconductor confinement layer

55 multiple quantum well active regions

56N type GaN semiconductor confinement layer

57N type GaN contact layer

58N electrode

specific implementation plan

Example 1:

As shown in Figure 4, the structure of the vertical light-emitting diode is: N electrode, N-type semiconductor window layer, N-type contact layer, N-type GaN semiconductor confinement layer, multi-quantum well active region, P-type GaN semiconductor The confinement layer, the P-type GaN contact layer and the P electrode are vertically connected sequentially from top to bottom. The N-type semiconductor window layer and the N-type contact layer are vertically connected to form a window layer structure for high light extraction.

本实施例中半导体窗口层的形状是倒梯形，也可以是圆柱形，或者立方体；N型接触层是N型InGaN半导体层或者超晶格结构SPS；Wherein the N-type semiconductor window layer is a transparent conductive material such as N-type ZnO or GaP, and the thickness of the semiconductor window layer is or greater than

In this embodiment, the shape of the semiconductor window layer is an inverted trapezoid, and may also be a cylinder, or a cube; the N-type contact layer is an N-type InGaN semiconductor layer or a superlattice structure SPS;

The method of its preparation process is as follows:

1. Laser lift off (LLO) or grinding and polishing etch to remove the substrate, making the LED into a vertical structure;

2. An N-type contact layer is epitaxially grown on the GaN epitaxial wafer without the sapphire lining. The N-type contact layer can be an N-type InGaN semiconductor layer or a superlattice structure SPS;

)的3. GaN epitaxial wafer and N-type semiconductor window layer (its thickness is

)of

surface cleaning;

4. Contact the GaN epitaxial wafer with the sapphire substrate removed and the N-type semiconductor window layer in methanol, put them into the bonding fixture and press them;

5. Apply pressure to the semiconductor window layer and the GaN epitaxial wafer with the sapphire substrate removed, and the semiconductor window layer and the GaN epitaxial wafer with the sapphire substrate removed together with the clamps are annealed in an N2 environment;

6. Preparation of P Electrode

7. Etching the N-type semiconductor window layer into an inverted trapezoidal shape

8. Deposit ITO as the current spreading layer of the N electrode to prepare the N electrode.

Example 2:

As shown in Figure 5, the structure of the vertical light-emitting diode is: P electrode, P-type semiconductor window layer, P-type contact layer, P-type GaN semiconductor confinement layer, multi-quantum well active region, N-type GaN semiconductor The confinement layer, the N-type GaN contact layer and the N electrode are vertically connected sequentially from top to bottom. The P-type semiconductor window layer and the P-type contact layer are vertically connected to form a window layer structure for high light extraction.

的其他值，其形状为圆柱形，也可以是倒梯形或者长方形。P型接触层是P型GaN半导体层，或者超晶格结构SPS；Wherein the P-type semiconductor window layer can be P-type ZnO, or transparent conductive materials such as P-type GaP, and the thickness of the semiconductor window layer in this embodiment is can also be greater than

For other values of , the shape is cylindrical, inverted trapezoidal or rectangular. The P-type contact layer is a P-type GaN semiconductor layer, or a superlattice structure SPS;

The method of its preparation process is as follows:

1. Cleaning the surface of the GaN epitaxial wafer and the semiconductor window layer of the sapphire substrate;

2. The two wafers are contacted and bonded in methanol, put into the bonding fixture and pressed tightly;

3. Apply pressure to the semiconductor window layer/GaN wafer, and the semiconductor window layer/GaN wafer is annealed in N2 environment together with the fixture;

4. Laser lift off (LLO) or grinding and polishing etch to remove the substrate, so that the LED becomes a vertical structure.

5. The etched semiconductor window layer is cylindrical in shape, and the thickness of the etched semiconductor window layer is

6. Preparation of P electrodes;

7. Deposit ITO as the current spreading layer of the N electrode to prepare the N electrode.

Claims (4)

1. the LED with vertical structure with high light extraction window comprises electrode, the window layer structure of high light extraction, contact layer, limiting layer, MQW active area; Electrode, the window layer structure of high light extraction, limiting layer, MQW active area, limiting layer, contact layer, electrode vertically connect from top to bottom successively; The polarity of electrode of MQW active area both sides is different; The electrode of MQW active area one side, the window layer structure of high light extraction and the polarity of limiting layer are identical, the limiting layer of MQW active area opposite side, the polarity of contact layer and electrode is identical.

2. the LED with vertical structure of a kind of high light extraction Window layer according to claim 1 is characterized in that: the window layer structure of described high light extraction connects and composes by semiconductor window layer is vertical with contact layer; Vertical connection of semiconductor window layer in electrode in the said Light-Emitting Diode and the window structure of described high light extraction, the vertical connection of limiting layer in the contact layer in the window structure of described high light extraction and the said Light-Emitting Diode.

3. a kind of LED with vertical structure with high light extraction Window layer according to claim 2 is characterized in that: the used material of said semiconductor window layer is the material of electrically conducting transparent.

4. a kind of LED with vertical structure with high light extraction Window layer as claimed in claim 2, its characteristic should be: the thickness of said semiconductor window layer is more than or equal to

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