Light emitting diode with improved luminous efficiency having a contact structure disposed on a frosted outer surface

• US 5,898,192 A
• Filed: 08/27/1996
• Issued: 04/27/1999
• Est. Priority Date: 10/09/1995
• Status: Expired due to Fees

• Current Assignee: Temic Telefunken Microelectronic GmbH (Continental AG)
• Original Assignee: Temic Telefunken Microelectronic GmbH (Continental AG)
• Inventors: Gerner, Jochen
• Primary Examiner(s): Jackson, Jerome
• Assistant Examiner(s): KELLEY, NATHAN K
• Application Number:
  US08/703,853
• Time in Patent Office: 973 Days
• Field of Search: 257/98, 257/81, 257/86, 257/91, 257/99
• US Class Current: 257/98
• CPC Class Codes: H01L 33/22 Roughened surfaces, e.g. at the interface between epitaxial layers
• CPC Class Codes: H01L 33/305 characterised by the doping materials
• CPC Class Codes: H01L 33/40 Materials therefor

Abstract

A light emitting diode for generating preferably green light with improved luminous efficiency. A number of epitaxial layers suitable for the light emission is arranged on a doped semiconductor substrate wafer of GaP. The surface of the epitaxial layers is completely frosted. The light emission from the interior is considerably improved by the frosting. A contact layer structure is placed on the frosted surface for contacting the light emitting diode. The contact layer consists of several partial layers and covers at least a part the frosted surface. There is also a contact layer at the rear of the light emitting diode.

Claims

1. Light emitting diode comprising a number of epitaxial layers suitable for light emission arranged on a semiconductor substrate, and a contact layer structure disposed on at least a part of the outer major surface of the epitaxial layers, and wherein:

the outer major surface of the epitaxial layers is completely frosted in order to increase the luminous efficiency,

the contact layer structure is arranged on the frosted surface, and

the roughness depth of the frosted surface is below 1 um.

2. Light emitting diode in accordance with claim 1, wherein the semiconductor substrate is made of doped gallium phosphide.

3. Light emitting diode in accordance with claim 2, wherein the doped gallium phosphide of the semiconductor substrate has (1 1 1) crystal orientation.

4. Light emitting diode in accordance with claim 3, wherein the epitaxial layers consist of an n-conductive layer of GaP arranged on the semiconductor substrate and a p-conductive layer of GaP arranged on the n-conductive layer.

5. Light emitting diode in accordance with claim 1, wherein the contact layer structure arranged on the frosted surface consists, in the sequence given, of a first contact layer of gold-zinc, a second contact layer of titanium-tungsten-nitride, and a third contact layer of aluminum.

6. Light emitting diode in accordance with claim 1, wherein the contact layer structure arranged on the frosted surface consists, in the sequence given, of a first contact layer of gold-zinc, a second contact layer of titanium-tungsten-nitride, and a third contact layer of aluminum-silicon.

7. Light emitting diode in accordance with claim 1, wherein the outer surface opposite to the frosted surface of the substrate is provided with a further contact layer made of a gold-germanium alloy.

8. Light emitting diode in accordance with claim 4, wherein the contact layer structure arranged on the frosted surface consists, in the sequence given, of a first contact layer of gold-zinc, a second contact layer of titanium-tungsten-nitride, and a third contact layer of aluminum.

9. Light emitting diode in accordance with claim 5, wherein the epitaxial layers consist of an n-conductive layer of GaP arranged on the semiconductor substrate and a p-conductive layer of GaP arranged on the n-conductive layer.

10. Light emitting diode in accordance with claim 4, wherein the contact layer structure arranged on the frosted surface consists, in the sequence given, of a first contact layer of gold-zinc, a second contact layer of titanium-tungsten-nitride, and a third contact layer of aluminum-silicon.

11. Light emitting diode in accordance with claim 6, wherein the epitaxial layers consist of an n-conductive layer of GaP arranged on the semiconductor substrate and a p-conductive layer of GaP arranged on the n-conductive layer.