DE202004012665U1 - Light-emitting diode arrangement based on a gallium nitride semiconductor compound - Google Patents

Abstract

Light-emitting diode arrangement based on a gallium nitride semiconductor compound, comprising at least:
a substrate (31);
an epitaxial layer resting on the substrate (31) and comprising, from bottom to top, an n-type GaN layer (32), an emission layer (33), and a p-type GaN layer (34);
a textured layer (36) provided above the p-type GaN layer (34);
a conductive translucent oxidation layer disposed on the textured layer (36) and making an ohmic contact with the textured layer (36);
a first electrode (38) electrically coupled to the conductive, light-transmissive oxidation layer; and
a second electrode (39) electrically coupled to the n-type GaN layer (32) of the epitaxial layer.

Description

The The invention relates to a light emitting diode array based on a gallium nitride semiconductor compound according to the preamble of claim 1.

A conventional light emitting diode array 10 based on a gallium nitride compound semiconductor, such as 1 can be seen, comprises a substrate 11 , a gallium nitride buffer layer (GaN buffer layer) 12 , an n-type GaN layer 13 , an indium gallium nitride (InGaN) layer 14 , a p-type GaN layer 15 , a p-type GaN contact layer 16 and a transparent conductive layer 17 , The layers of 12 to 16 form an epitaxial layer. A metallic p-type electrode 18 lies on the transparent conductive layer 17 on while a metallic n-type electrode 19 on the n-type GaN layer 13 rests.

It has long been known that the p-type GaN contact layer 16 has a poor conductivity. This means that the electric current is below the metallic p-type electrode 18 is limited. In order to enable uniform emission by effectively scattering the electric current, the transparent conductive layer must 17 on the p-type GaN contact layer 16 be applied in a nationwide way. In order to increase the light transmission, the transparent conductive layer must 17 but be very thin. Conventionally used, transparent conductive layer 17 is made of nickel or gold (Au). In order to increase the efficiency of light extraction, a textured configuration must form on the surface of the light emitting diode. Using the thin, transparent conductive layer 17 nickel or gold, however, results in unevenness of the current distribution in the transverse direction. In particular, it is disadvantageous that a local emission occurs, which causes an increase in the operating voltage (see 4 ).

The known indium tin oxide (ITO) is a material with a large energy gap between 2.9 and 3.8 volts. In the field of visible light, ITO has one Penetration degree over 95% up. Besides that is ITO a highly conductive n-type material, and the refractive index of ITO is in the range from 1.7 to 2.2. Due to the refractive index (n = 2,4) of the Epitaxial layer and the refractive index (n = 1.5) of the packaging resin material becomes in accordance with Snell law and anti-reflection principle a reduction of light reflection and thus an increase ensures the light, if an agent with a refractive index of n = 1.9 is added can. Therefore, this means (ITO) as a window layer of the light emitting diode serve.

In a Taiwanese patent application (TW 461126), an idea has been proposed that ITO be used as a transparent conductive layer. As in 2 shown has a diode array 20 a substrate 21 , a GaN buffer layer 22 , an n-type GaN layer 23 , an InGaN active layer 24 , a p-type GaN layer 25 , a p-type GaN contact layer 26 , a transparent conductive oxidation layer 27 , a p-type electrode 24 and an n-type electrode 29 on. The transparent conductive oxidation layer 27 While it is an ITO for facilitating light harvesting, it is hardly possible to make a good ohmic contact with ITO when the surface of the p-type GaN contact layer located below 26 is a flat Ga-polarized surface. This then results in a high contact resistance and leads to a bad ohmic contact, whereby the operating voltage of the LEDs is difficult to reduce.

Out For this reason, in view of the disadvantages of the present inventor Solutions, based on longtime Experience in this area, after a long study, numerous experiments and unceasing improvements to the present invention.

By The invention will be a light emitting diode array based on a gallium nitride semiconductor compound created in the case of a conductive, transparent oxidation layer a gallium nitride layer provided with a textured layer above is attached and serves as a window layer, wherein the textured Layer as ohmic contact layer to the conductive, transparent oxidation layer usable, resulting in effective reduction of contact resistance and the operating voltage causes the textured layer for the Interruption of the light guiding ensures the efficiency of the Increase light production and thus to improve the quantum yield.

The Invention has in particular the features specified in claim 1 on. In the dependent claims embodiments of the invention are given.

in the Following are objects, features and operation of the invention based on a preferred embodiment and the accompanying drawings be explained in more detail. Show it:

1 a sectional view of a conventional light emitting diode array based on a gallium nitride compound semiconductor;

2 a sectional view of a conventional light emitting diode array based on a Indiumgalliumnitrid semiconductor compound;

3 a sectional view of a light emitting diode array based on a gallium nitride semiconductor compound according to the invention;

4 a current-voltage curve of the combination of a conductive translucent nickel / Au layer and a textured surface; and

5 a current-voltage curve of a combination of a conductive, translucent ITO layer and a textured surface.

Referring to 3 The light-emitting diode arrangement according to the invention based on a gallium nitride semiconductor compound comprises a substrate from bottom to top 31 , an n-type GaN layer 32 , an emission layer 33 , a p-type GaN layer 34 , a p-type contact layer 35 , a textured layer 36 , a window layer 37 , a first electrode 38 and a second electrode 39 , There is also a buffer layer 31 ' on the substrate 31 ,

The n-type GaN layer 32 , the emission layer 33 and the p-type GaN layer 34 form an epitaxial layer provided according to the invention, which is attached to the substrate 31 is coupled. In addition, there is the textured layer 36 above the p-type GaN layer 34 and the p-type contact layer 35 , A conductive, translucent oxidation layer above the textured layer 36 is called a window layer 37 used and forms with the textured layer 36 an ohmic contact. In addition, the first and second electrodes 38 . 39 to the conductive, translucent oxidation layer or to the n-type GaN layer 32 the epitaxial layer is electrically connected.

The substrate 31 is selected from a group comprising sapphire, zinc oxide, lithium gallium oxide, lithium aluminum oxide, spinel, silicon carbide, gallium arsenide and silicon substrates. The n-type GaN layer 32 is selected from a group comprising an n-doped gallium nitride, AlInGaN and InGaN layer. The p-type GaN layer 34 is selected from a group comprising a p-doped gallium nitride, AlInGaN and InGaN layer. The emission layer 33 is a nitride semiconductor with indium. The window layer 37 is a conductive, translucent oxidation layer selected from the group consisting of indium oxide, tin oxide, indium-molybdenum oxide, zinc oxide, indium-tin oxide layer.

The provision of the textured layer 36 between the p-type contact layer 35 and the window layer 37 causes an increase in light production. Due to their rough surface results in an increase of the emission and an interruption of the light-guiding effect. When the semiconductor layers are grown, their surface can be maintained in the nitrogen polarized state as disclosed in the Taiwanese patent application (TW 92136888) and for the reduction of the contact resistance between the window layer 37 and the p-type GaN layer 34 ensures to allow formation of the excellent ohmic contact layer.

In addition, the operating voltage of the diodes can be reduced (see 5 ). Furthermore, the textured layer 36 selected from a group comprising n-, p-doped and double-doped gallium nitride layer.

10

LED array

11

substratum

12

GaN buffer layer

13

n-type GaN layer

14

InGaN layer

15

p-type GaN layer

16

p-type GaN contact layer

17

transparent conductive layer

18

metallic p-type electrode

19

metallic n-type electrode

20

diode array

21

substratum

22

GaN buffer layer

23

n-type GaN layer

24

InGaN active layer

25

p-type GaN layer

26

p-type GaN contact layer

27

transparent conductive oxidation layer

28

p-type electrode

29

n-type electrode

30

led

31

substratum

31 '

buffer layer

32

n-type GaN layer

33

emission layer

34

p-type GaN layer

35

p-type contact layer

36

textured layer

37

window layer

38

first electrode

39

second electrode

Claims (5)

Light-emitting diode arrangement based on a gallium nitride semiconductor compound, comprising at least: a substrate ( 31 ); an epitaxial layer deposited on the substrate ( 31 ) and from bottom to top an n-type GaN layer ( 32 ), an emission layer ( 33 ) and a p-type GaN layer ( 34 ); a textured layer ( 36 ) above the p-type GaN layer ( 34 ) is provided; a conductive, translucent oxidation layer deposited on top of the textured layer ( 36 ) and with the textured layer ( 36 ) forms an ohmic contact; a first electrode ( 38 ) electrically coupled to the conductive, translucent oxidation layer; and a second electrode ( 39 ) attached to the n-type GaN layer ( 32 ) the epitaxial layer is electrically coupled. Light-emitting diode arrangement according to claim 1, characterized in that the textured layer ( 36 ) is selected from a group comprising n-, p-doped and double-doped gallium nitride layers. Light-emitting diode arrangement according to Claim 1, characterized that a conductive, translucent Oxidation layer is selected from the group consisting of indium oxide, tin oxide, Indium molybdenum oxide, Zinc oxide, indium tin oxide layer has. Light-emitting diode arrangement according to claim 1, characterized in that the emission layer ( 33 ) is formed as a nitride semiconductor with indium. Light-emitting diode arrangement according to claim 1, characterized in that the textured layer ( 36 ) is formed as a nitrogen-polarized surface layer.