Light emitting diode having multiple pits

• US 6,885,034 B1
• Filed: 05/06/2004
• Issued: 04/26/2005
• Est. Priority Date: 05/09/2003
• Status: Expired due to Fees

• Current Assignee: Winston Vaughan Schoenfeld
• Original Assignee: Winston Vaughan Schoenfeld
• Inventors: Schoenfeld, Winston Vaughan
• Primary Examiner(s): CRANE, SARA W
• Application Number:
  US10/840,695
• Time in Patent Office: 355 Days
• Field of Search: 257/98, 257/99, 257/79, 438/42, 438/43
• US Class Current: 257/98
• CPC Class Codes: H01L 33/20 with a particular shape, e.g. curved or truncated substrate
• CPC Class Codes: H01L 33/22 Roughened surfaces, e.g. at the interface between epitaxial layers

Abstract

The light extraction efficiency of a Light Emitting Diode (LED) is improved by providing pits etched into a top, emitting, surface of the LED. The presence of the pits reduces the mean distance to a sidewall in active regions, and creates regions of higher transmission at which a semi-transparent contact is not present. The walls of the pits are preferably coated with a passivating layer, such as silicon dioxide, to reduce surface leakage currents and to improve the operational stability of the device at the expense of a reduction in optical extraction efficiency commonly obtained with encapsulants having a higher index of refraction.

Claims

1. A light emitting diode comprising:

a die having parallel top and bottom surfaces and a plurality of sidewalls;

an active region parallel to the top and bottom surfaces;

a plurality of pits, each extending from the top surface through the active region so as to define at least a respective sidewall; and

a passivating layer covering the sidewalls so that no part of the active layer is exposed to a non-passivated surface.

2. The diode of claim 1 further comprising a semi-transparent contact layer disposed on the top surface of the die.

3. The diode of claim 1 wherein the passivating layer comprises sputter-deposited silicon dioxide.

4. The diode of claim 1 wherein the passivating layer has an optical index of refraction that is less than 1.5.

5. A method of making a light emitting diode structure comprising the sequentially executed steps of:

a) providing a light emitting diode die having parallel top and bottom surfaces, a plurality of sidewalls, a semitransparent electrode film extending across the top surface, and an active region disposed between and parallel to the top and bottom surfaces;

b) forming a plurality of pits in the top surface, each of the pits extending from the top surface through the active region, each of the pits comprising at least one respective sidewall;

c) sputter-depositing a passivating layer to cover the semi-transparent electrode and all the sidewalls;

e) exposing at least a portion of the semi-transparent electrode; and

f) depositing a metallic contact on at least a portion of the semitransparent electrode.

6. The process of claim 5 wherein the step of forming the plurality of pits comprises sub-steps of:

b1) applying a photoresist layer and photolithographically defining a plurality of pit locations; and

b2) reactive-ion etching into the die at each of the pit locations so as to form the plurality of pits.

7. The process of claim 5 wherein the step of exposing at least a portion of the semitransparent electrode comprises substeps of:

e1) photolithographically defining openings in the passivating layer; and

e2) etching away the portions of the passivating layer within the openings.