Enhanced light extraction in LEDs through the use of internal and external optical elements

• US 6,821,804 B2
• Filed: 09/17/2003
• Issued: 11/23/2004
• Est. Priority Date: 12/03/1999
• Status: Expired due to Term

• Current Assignee: Creeled Incorporated
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Mack, Michael, DenBaars, Steven, Thibeault, Brian
• Primary Examiner(s): Tran, Minhloan
• Assistant Examiner(s): FORDE, REMMON R
• Application Number:
  US10/665,595
• Publication Number:
  US 20040041164A1
• Time in Patent Office: 433 Days
• Field of Search: 438/29, 438/23, 438/22, 438/24, 438/32, 438/42, 438/44, 257/98, 257/99, 257/94, 257/95
• US Class Current: 438/29
• CPC Class Codes: H01L 2933/0091 Scattering means in or on the semiconductor body or semiconductor body package H01L33/22 takes precedence
• 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
• CPC Class Codes: H01L 33/44 characterised by the coatings, e.g. passivation layer or anti-reflective coating
• CPC Class Codes: Y10S 977/712 formed from plural layers of nanosized material, e.g. stacked structures
• CPC Class Codes: Y10S 977/834 Optical properties of nanomaterial, e.g. specified transparency, opacity, or index of refraction

Abstract

This invention describes new LEDs having light extraction structures on or within the LED to increase its efficiency. The new light extraction structures provide surfaces for reflecting, refracting or scattering light into directions that are more favorable for the light to escape into the package. The structures can be arrays of light extraction elements or disperser layers. The light extraction elements can have many different shapes and are placed in many locations to increase the efficiency of the LED over conventional LEDs. The disperser layers provide scattering centers for light and can be placed in many locations as well. The new LEDs with arrays of light extraction elements are fabricated with standard processing techniques making them highly manufacturable at costs similar to standard LEDs. The new LEDs with disperser layers are manufactured using new methods and are also highly manufacturable.

Claims

1. A method for growing a light emitting diode having an internal disperser layer to enhance light extraction, comprising:

placing a substrate in a reactor for growing semiconductor materials;

growing a first semiconductor layer on said substrate, said first layer having a rough surface;

stopping growth of said semiconductor layer;

growing a disperser layer of semiconductor material on said roughened layer, said disperser layer having a different index of refraction than said first layer;

growing a second layer on said disperser layer, said second layer having a similar index of refraction as said first layer; and

growing a semiconductor light emitting structure on said second layer.

2. The method of claim 1, wherein said light emitting diode is AlInGaN based and said first layer is grown rough by increasing the flow of disiline, changing the flow of ammonia, or increasing the rate that said first layer is grown.

3. The method of claim 1, wherein said light emitting diode has a first spreading layer and said disperser layer is grown within said spreading layer.

4. A method for manufacturing an AlInGaN light emitting diode with an internal disperser layer to enhance light extraction, comprising:

placing a substrate in a reactor for growing semiconductor materials;

growing uncoalesced islands of material made of Al_xIn_yGa_1-x-yN, 0≦

x≦

1, 0≦

y≦

1, on said substrate;

stopping the growth of islands;

depositing a disperser layer on said uncoalesced islands, said disperser layer having a different index of refraction from said highly doped GaN material;

growing a layer of material made of Al_xIn_yGa_1-x-yN, 0≦

x≦

1, 0≦

y≦

1, on said disperser layer, said layer having a smooth surface; and

growing a light emitting structure on said layer.