Formation of ohmic contacts in III-nitride light emitting devices

• US 6,657,300 B2
• Filed: 01/05/2001
• Issued: 12/02/2003
• Est. Priority Date: 06/05/1998
• Status: Expired due to Term

• Current Assignee: Lumileds LLC (Apollo Global Management, Inc.)
• Original Assignee: Lumileds Lighting US LLC (Apollo Global Management, Inc.)
• Inventors: Christenson, Gina L., Chen, Changhua, Goetz, Werner K., Camras, Michael D., Steigerwald, Daniel A., Kern, R. Scott, Kuo, Chihping, Martin, Paul Scott
• Primary Examiner(s): CRANE, SARA W
• Application Number:
  US09/755,935
• Publication Number:
  US 20020008243A1
• Time in Patent Office: 1,061 Days
• Field of Search: 257/744, 257/745, 257/94, 257/96, 257/97, 257/102, 257/103
• US Class Current: 257/745
• 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 Ωcm 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 III-nitride 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 of GaN, formed over the p-type Al_xGa_(1-x)N layer, the p-type transition layer having a resistivity of about 100 Ω

cm; 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. A light-emitting diode comprising:

a substrate;

an n-type layer of III-nitride 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 having a resistivity from about 7 Ω

cm to about 250 Ω

cm; 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.

3. The light emitting diode of claim 2 wherein the p-type transition layer further comprises at least one Group II dopant selected from Be, Mg, Ca, Sr, Zn, Cd, and C.

4. The light emitting diode of claim 3 wherein the Group II dopant is Mg and wherein the p-type transition layer further comprises a co-dopant selected from Si, Ge, O, S, Se, and Te.

5. The light emitting diode of claim 4 wherein the concentration of Mg exceeds about 5e10¹⁹ cm⁻

3 in the p-type transition layer.

6. The light emitting diode of claim 2 wherein the p-type transition layer is a III-V material.

7. The light emitting diode of claim 2 wherein the p-type transition layer is selected from GaN, AlInGaN, InGaN, GaNAs, GaNP, AlInGaNAsP, and GaNAsP.

8. The light emitting diode of claim 2 further comprising a p-type conductivity layer of GaN, formed over the p-type Al_xGa_(1-x)N layer.

9. The light emitting diode of claim 2 wherein a driving voltage of the light emitting diode is less than about 3.5 volts.