Laser roughening to improve led emissions
AssigneePalo Alto Research Center Incorporated
InventorsClifford F. Knollenberg, David P. Bour, Christopher L. Chua, Jeng Ping Lu
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Abstract
An improved method of forming a LED with a roughened surface is described. Traditional methods of roughening a LED surface utilizes strong etchants that require sealing or protecting exposed areas of the LED. The described method uses a focused laser to separate the LED from the substrate, and a second laser to roughen the LED surface thereby avoiding the use of strong etchants. A mild etchant may be used on the laser roughened LED surface to remove unwanted metals.
Claims19
A method of roughening a LED surface to improve light extraction efficiency comprising the operations of:
- forming a LED structure over a substrate;
- using a first laser to generate sufficient heat between the LED structure and the substrate to cause separation of the LED structure from the substrate in a laser lift off process;
- using a focused second laser with a spot size less than 0.01 mm2 to produce a series of small pits in a surface of the LED structure that was previously attached to the substrate thereby creating a pitted surface.
The method of claim wherein a depth of each pit is approximately between 100 nm and 2000 nm.
A method of roughening a LED surface to improve light extraction efficiency comprising the operations of:
- forming a n-doped layer over a substrate,
- forming an active region of the n-doped layer, the active region to emit light;
- using a first defocused laser delivering a power per unit area of less than 2 J/cm2 to separate the n-doped layer from the substrate in a laser lift off process and to create a laser lift off surface of the n-doped layer;
- using a second focused laser delivering a power per unit area in excess of 2 J/cm2 to pit the laser lift off surface of the n-doped layer.
Dependencies are inferred from the claim text.