Increased efficiency LED

• US 5,705,834 A
• Filed: 04/23/1996
• Issued: 01/06/1998
• Est. Priority Date: 04/23/1996
• Status: Expired due to Fees

• Current Assignee: Analytical Services And Materials, Inc., National Aeronautics and Space Administration (Government of the United States of America)
• Original Assignee: United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration
• Inventors: Egalon, Claudio O., Rogowski, Robert S.
• Primary Examiner(s): Crane, Sara W.
• Assistant Examiner(s): Wille, Douglas A.
• Application Number:
  US08/644,654
• Time in Patent Office: 623 Days
• Field of Search: 257/13, 257/79, 257/82, 257/88, 257/84, 257/95, 257/96, 257/98
• US Class Current: 257/95
• CPC Class Codes: H01L 33/20 with a particular shape, e.g. curved or truncated substrate

Abstract

In an LED a large portion of the light produced is lost due to total internal reflection at the air-semiconductor interface. A reverse taper of the semiconductor is used to change the angle at which light strikes the interface so that a greater portion of the light is transmitted.

Claims

1. A light emitting diode comprising:

two semiconductor regions forming a light producing diode junction;

a light emitting end face;

a first one of the two semiconductor regions forming an outer volume, surrounding a second of the two semiconductor regions;

a base, opposed to the light emitting end face;

a plurality of sides of the outer volume, the sides connecting the light emitting end face to the base;

the sides further defining a reverse taper such that the cross sectional area of the light emitting diode is greater at the light emitting end face than at the base.

2. A light emitting diode according to claim 1 wherein the sides are curved to produce a curved reverse taper.

3. A light emitting diode according to claim 1 further comprising:

a layer having an index of refraction between that of the light emitting diode at the light emitting end face and that of a medium in which the light emitting diode is to be operated;

the layer directly optically connected to the light emitting end face.

4. A light emitting diode according to claim 3 wherein the sides are curved to produce a curved reverse taper.

5. A light emitting diode according to claim 3 wherein the layer is chosen to be of a shape such that it continues the reverse taper of the light emitting diode.