Electrical current distribution in light emitting devices

• US 8,124,994 B2
• Filed: 09/04/2007
• Issued: 02/28/2012
• Est. Priority Date: 09/04/2006
• Status: Expired due to Fees

• Current Assignee: Tinggi Technologies Pte., Ltd.
• Original Assignee: Tinggi Technologies Pte., Ltd.
• Inventors: Yuan, Shu, Lin, Shiming
• Primary Examiner(s): WRIGHT, TUCKER J
• Application Number:
  US12/440,019
• Publication Number:
  US 20100117107A1
• Time in Patent Office: 1,638 Days
• Field of Search: 257/E33.066, 257/E33.067, 257/E33.068, 257 79-103, 438 29- 32, 438/34
• US Class Current: 257/98
• CPC Class Codes: H01L 24/97 the devices being connected to a common substrate, e.g. interposer, said common substrate being separable into individual assemblies after connecting
• CPC Class Codes: H01L 2924/12041 LED
• CPC Class Codes: H01L 2924/3011 Impedance
• CPC Class Codes: H01L 2933/0016 relating to electrodes
• CPC Class Codes: H01L 33/20 with a particular shape, e.g. curved or truncated substrate
• CPC Class Codes: H01L 33/38 with a particular shape

Abstract

A light emitting device is disclosed that has a plurality of epitaxial layers including an active layer, at least one of a reflective layer and an ohmic contact on a first side of the epitaxial layers; and a layer of a conductive metal on a second side of the epitaxial layers and having a light emitting surface. A terminal is on the light emitting surface, the terminal comprising an array for diffusing electrical current and minimizing its effect on light output. The array may have a bonding pad, an outer portion, and a joining portion connecting the bonding pad and the outer portion; the outer portion and the joining portion being for current dissipation.

Claims

1. A light emitting device comprising:

a plurality of epitaxial layers including an active layer;

a reflective layer on a first side of the epitaxial layers;

a layer of a conductive metal on a second side of the epitaxial layers and having a light emitting surface;

a terminal comprising an array on the light emitting surface, the array being for diffusing electrical current and minimizing its effect on light output; and

a second reflective layer of a same shape and dimensions as the array, the second reflective layer being beneath the array on the light emitting surface or at a bottom of a trench in the light emitting surface, the second reflective layer being for reflecting light propagated by the active layer under the array and being electrically conductive to enable electric current to pass from the array to the active layer, the second reflective layer including a diffusing surface to reflect the light propagated by the active layer at an angle other than perpendicular to the reflective layer.

2. The light emitting device as claimed in claim 1, wherein the array comprises a bonding pad, an outer portion, and a joining portion connecting the bonding pad and the outer portion;

the outer portion and the joining portion being for current dissipation.

3. The light emitting device as claimed in claim 2, wherein the outer portion is at or adjacent a periphery of the light emitting surface.

4. The light emitting device as claimed in claim 2, wherein the joining portion comprises a plurality of spokes joining the bonding pad and the outer portion.

5. A method of fabricating a light emitting device comprising a plurality of epitaxial layers including an active layer, a reflective layer on a first side of the epitaxial layers and a conductive metal on a second side of the epitaxial layer, the conductive metal having a light emitting surface;

the method comprising;

forming a second reflective layer on the light emitting surface or at a bottom of a trench in the light emitting surface; and

forming a terminal comprising an array on the second reflective layer, the array being for diffusing electrical current and minimizing its effect on light output;

the second reflective layer being of a same shape and dimensions as the array, the second reflective layer also for reflecting light propagated by the active layer under the array and being electrically conductive to enable electric current to pass from the array to the active layer, and the second reflective layer including a diffusing surface to reflect light propagated by the active layer at an angle other than perpendicular to the reflective layer.

6. The method in claim 5, wherein the forming of the array is by forming a bonding pad, an outer portion, and a joining portion electrically connecting the bonding pad and the outer portion;

the outer portion and the joining portion being for current dissipation.

7. The method as claimed in claim 6, wherein the outer portion is at or adjacent a periphery of the light emitting surface.

8. The method as claimed in claim 6, wherein the joining portion comprises a plurality of spokes joining the bonding pad and the outer portion.