Formation of Ohmic contacts in III-nitride light emitting devices

• US 20050167693A1
• Filed: 03/30/2005
• Published: 08/04/2005
• Est. Priority Date: 06/05/1998
• Status: Active Grant

• Current Assignee: Lumileds LLC (Apollo Global Management, Inc.)
• Original Assignee: Lumileds Lighting US LLC (Apollo Global Management, Inc.)
• Inventors: Chen, Xiaoping, Goetz, Werner K., Camras, Michael D., Steigerwald, Daniel A., Kern, R. Scott, Christenson, Gina L., Kuo, Chihping, Martin, Paul Scott, Chen, Changhua
• Granted Patent: US 7,345,323 B2
• Time in Patent Office: Days
• US Class Current: 257/103
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: H01L 33/32 containing nitrogen
• CPC Class Codes: H01L 33/40 Materials therefor
• CPC Class Codes: H01S 5/0421 characterised by the semiconducting contacting layers electrodes H01S5/0425
• CPC Class Codes: H01S 5/04257 having positive and negative electrodes on the same side of the substrate
• CPC Class Codes: H01S 5/32341 blue laser based on GaN or GaP

Abstract

P-type layers of a GaN based light-emitting device are optimized for formation of Ohmic contact with metal. In a first embodiment, a p-type GaN transition layer with a resistivity greater than or equal to about 7 Ω cm is formed between a p-type conductivity layer and a metal contact. In a second embodiment, the p-type transition layer is any III-V semiconductor. In a third embodiment, the p-type transition layer is a superlattice. In a fourth embodiment, a single p-type layer of varying composition and varying concentration of dopant is formed.

Claims

1. A light-emitting diode comprising:

a substrate;

an n-type layer of GaN formed over the substrate;

an active region, formed over the n-type layer;

a p-type Al_xGa_(1-x)N (0≦

x≦

1) layer, formed over the active region;

a p-type transition layer, formed over the p-type Al_xGa_(1-x)N layer, the p-type transition layer comprising a superlattice, the superlattice further comprising;

a first sublayer of doped p-type material;

a second sublayer of material, wherein a concentration of dopant in the second sublayer is less than a concentration of dopant in the first sublayer; and

an n-type contact and a p-type contact, the n-type contact being connected to the n-type layer, the p-type contact being connected to the p-type transition layer.

2. The light-emitting diode of claim 1 wherein the dopant is Mg and the dopant concentration of the first sublayer is about 1 e20 cm⁻

3 to about 5e21 cm<sup>−

3</sup>.

3. The light-emitting diode of claim 1 wherein the dopant is Mg and the dopant concentration of the second sublayer is undoped to about 1 e20 cm⁻

3.

4. The light-emitting diode of claim 1 wherein each of the first and second sublayers has a thickness from about 2 to about 20 nm.

5. The light emitting diode of claim 1 wherein a driving voltage of the light emitting diode is less than about 3.5 volts.

6. A light emitting diode comprising:

a substrate;

an n-type layer of GaN formed over the substrate;

an active region, formed over the n-type layer;

a p-type Al_xGa_(1-x)N (0≦

x≦

1) layer, formed over the active region;

a p-type transition layer, formed over the p-type Al_xGa_(1-x)N layer, the p-type transition layer comprising a sublayer of a p-type doped material and a sublayer of elemental dopant; and

an n-type contact and a p-type contact, the n-type contact being connected to the n-type layer, the p-type contact being connected to the p-type transition layer.

7. The light emitting diode of claim 6 wherein the dopant is Mg.

8. The light emitting diode of claim 6 further comprising a p-type conductive layer of GaN, formed over the p-type Al_xGa_(1-x)N layer.

9. The light emitting diode of claim 6 wherein a driving voltage of the light emitting diode is less than about 3.5 volts.