Substrate-free light emitting diode chip

Abstract

A light emitting diode (LED) chip has a multilayer semiconductor structure that is at least 10 microns thick and does not require an attached growth substrate or transfer substrate for structural rigidity or support. The multilayer semiconductor structure includes a first doped layer, a second doped layer and an active region interposed between the first doped layer and the second doped layer. Optionally, the multilayer semiconductor structure includes an undoped layer. At least one of the layers of the multilayer semiconductor structure is at least 5 microns thick and is preferably deposited by hydride vapor phase epitaxy.

Description

REFERENCE TO PRIOR APPLICATION[0001]This application claims the benefit of U.S. Provisional Patent Application Ser. No. 61 / 005,258, which was filed on Dec. 3, 2007, and which is herein incorporated by reference.TECHNICAL FIELD[0002]The present invention is a thick light emitting diode chip. The chip is substrate-free or free-standing and requires no growth substrate or transfer substrate for structural support.BACKGROUND OF THE INVENTION[0003]Conventional light emitting diodes (LEDs) are fabricated by epitaxially growing multiple layers of semiconductors on a growth substrate. Inorganic light-emitting diodes can be fabricated from GaN-based semiconductor materials containing, for example, gallium nitride (GaN), aluminum nitride (AlN), aluminum gallium nitride (AlGaN), indium nitride (InN), indium gallium nitride (InGaN) and aluminum indium gallium nitride (AlInGaN). Other appropriate materials for LEDs include, for example, aluminum gallium indium phosphide (AlGaInP), gallium arseni...

AI Technical Summary

Benefits of technology

[0012]A substrate-free or free-standing LED chip of this invention is an LED chip that does not include a growth substrate or transfer substrate as an element of the LED chip. The growth substrate is defined as the substrate onto which the multilayer semiconductor structure is epitaxially grown. For LED chips of this invention, the growth substrate is removed after the multilayer semiconductor structure is fabricated and no transfer substrate is permanently bonded to the multilayer semiconductor structure prior to the removal of the growth substrate. The LED chips of this invention have multilayer semiconductor structures that are at least 10 microns thick and do not require an attached growth substrate or transfer substrate for structural rigidity or support. The LED chips can be handled without damage and without breaking.

[0015]An LED chip that has both electrodes on the first side or the second side of the multilayer semiconductor structure may optionally include a substantially undoped layer on the side of the multilayer semiconductor structure opposite the electrodes. The undoped layer can add additional thickness to the multilayer semiconductor structure without affecting the electrical properties of the structure. The additional thickness adds to the structural strength of the multilayer semiconductor structure. In addition, the heat transfer characteristics of an additional undoped layer fabricated from the same semiconductor material (for example, gallium nitride) as the remainder of the multilayer semiconductor structure will be better than the heat transfer characteristics of a growth substrate or transfer substrate of the prior art made from a different material.

[0016]The multilayer semiconductor structure of the thick LED chip has at least one thick semiconductor layer to provide structural support to the chip. The thick semiconductor layer can be the first doped layer, the second doped layer, the optional undoped layer or a combination of two or more thick layers. The thick semiconductor layers preferably are fabricated by hydride vapor phase epitaxy (HVPE). Each thick semiconductor layer is at least 5 microns thick, preferably at least 10 microns thick, more preferably at least 15 microns thick and most preferably at least 25 microns thick. When the LED chip includes at least one thick semiconductor layer to provide structural support, the growth or transfer substrate is no longer needed and the LED chip can be handled as a substrate-free or free-standing device without damage.

Problems solved by technology

However, none of these additional surfaces, submounts, heat sinks, leadframes or other structures are elements of the LED chip.

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