Chip shaping for flip-chip light emitting diode

• US 6,784,460 B2
• Filed: 10/10/2002
• Issued: 08/31/2004
• Est. Priority Date: 10/10/2002
• Status: Expired due to Term

• Current Assignee: Document Security Systems, Inc.
• Original Assignee: Agilent Technologies, Inc.
• Inventors: Ng, Kee Yean, Kuan, Yew Cheong
• Primary Examiner(s): Flynn, Nathan J.
• Assistant Examiner(s): MANDALA, VICTOR A
• Application Number:
  US10/268,223
• Publication Number:
  US 20040070000A1
• Time in Patent Office: 691 Days
• Field of Search: 257/80, 257/81, 257/82, 257/94, 257/95, 257/98, 257/99, 257/100, 257/680
• US Class Current: 257/95
• CPC Class Codes: H01L 33/20 with a particular shape, e.g. curved or truncated substrate

Abstract

A LED of flip-chip design comprises a light emitting region and one or more transparent substrates overlying the light emitting region. The light emitting region includes a negatively doped layer, a positively doped layer, and an active p-n junction layer between the negatively doped layer and the positively doped layer. At least one of the substrates has a pyramidal shape determined by (1) the composition of electrically conductive or electrically non-conductive material, (2) the number of side surfaces, (3) the degree of offset of an apex or top surface, and (4) the slope angle of each side surface relative to a bottom surface.

Claims

1. A semiconductor light-emitting diode of flip-chip design, comprising:

a light-emitting region including a negatively doped layer, a positively doped layer, and an active p-n junction layer between said negatively doped layer and said positively doped layer;

a transparent substrate overlying said light-light emitting region, said substrate having a pyramidal shape so that said substrate has a cross-sectional area that decreases with distance from said junction and wherein lateral extent of said substrate is bound by lateral extent of a doped layer nearest to the transnarent substrate; and

ohmic contacts for forward biasing said junction layer so that at least most of the light is emitted from the junction layer into the surrounding environment is emitted through said substrate.

2. The semiconductor light emitting diode of claim 1,

wherein said substrate has a side surface and a bottom surface, and

wherein a slope angle of said side surface relative to said bottom surface is within a range of 10-80 degrees.

3. The semicunductor light emitting diode of claim 1, wherein said substrate is composed of electricity non-conductive material.

4. The semiconductor light emitting diode of claim 1, wherein said substrate has a truncated pyramidal shape so as to define a flat top surface through which at least some of said light is emitted into said surrounding environment.

5. The semiconductor light emitting diode of claim 4, wherein said top surface has a center coinciding with a center longitudinal axis of said substrate.

6. A semiconductor light-emitting diode of flip-chip design, comprising:

a light-emitting region including a first doped layer, a second doped layer, and an active p-n junction layer between said first doped layer and said second doped layer; and

a first transparent substrate adjacent said first doped layer, said first transparent substrate having a pyramidal shape that said substrate has a cross-sectional area that decreases with distance from said junction and wherein lateral extent of said substrate is bound by lateral extent of a doped layer nearest to the transparent substrate; and

ohmic contacts for forward biasing said junction layer so that at least most of the light is emitted from the junction layer into the surrounding environment is emitted through said substrate.

7. The semiconductor light emitting diode of claim 6,

wherein said first transparent substrate has a side surface and a bottom surface, and

wherein a slope angle of said side surface relative to said bottom surface is within a range of 1-80 degrees.

8. A semiconductor light-emitting diode of flip-chip design, comprising:

a light-emitting region including a first doped layer, a second doped layer, and an active p-n junction layer between said first doped layer and said second doped layer; and

a first transparent substrate adjacent said first doped layer, said first transparent substrate having a pyramidal shape that said substrate has a cross-sectional area that decreases with distance from said junction and wherein lateral extent of said substrate is bound by lateral extent of said first doped layer; and

ohmic contacts for forward biasing said junction layer so that at least most of the light is emitted from the junction layer into the surrounding environment is emitted through said substrate; and

wherein an upper portion of said first doped layer has a pyramidal shape.