North Carolina State University

Darren B Thomson

Thomas Gehrke

Kevin J Linthicum

Robert F Davis

Pradeep Rajagopal

Eric Porter Carlson

Tsvetanka Zheleva

Scott A Smith

Kieran M Tracy

An underlying gallium nitride layer on a silicon carbide substrate is masked with a mask that includes an array of openings therein, and the underlying gallium nitride layer is etched through the array of openings to define posts in the underlying gallium nitride layer and trenches therebetween. The posts each include a sidewall and a top having the mask thereon. The sidewalls of the posts are laterally grown into the trenches to thereby form a gallium nitride semiconductor layer. During this lateral growth, the mask prevents nucleation and vertical growth from the tops of the posts. Accordingly, growth proceeds laterally into the trenches, suspended from the sidewalls of the posts. The sidewalls of the posts may be laterally grown into the trenches until the laterally grown sidewalls coalesce in the trenches to thereby form a gallium nitride semiconductor layer. The lateral growth from the sidewalls of the posts may be continued so that the gallium nitride layer grows vertically through the openings in the mask and laterally overgrows onto the mask on the tops of the posts, to thereby form a gallium nitride semiconductor layer. The lateral overgrowth can be continued until the grown sidewalls coalesce on the mask to thereby form a continuous gallium nitride semiconductor layer. Microelectronic devices may be formed in the continuous gallium nitride semiconductor layer.

Pendeoepitaxial gallium nitride semiconductor layers on silicon carbide substrates

A gallium nitride layer is laterally grown into a trench in the gallium nitride layer, to thereby form a lateral gallium nitride semiconductor layer. At least one microelectronic device may then be formed in the lateral gallium nitride semiconductor layer. Dislocation defects do not significantly propagate laterally into the lateral gallium nitride semiconductor layer, so that the lateral gallium nitride semiconductor layer is relatively defect free.

Methods of fabricating gallium nitride semiconductor layers by lateral growth into trenches

Second gallium nitride layers that extend into trenches in first gallium nitride layers

A gallium nitride microelectronic layer is fabricated by converting a surface of a (111) silicon layer to 3C-silicon carbide. A layer of 3C-silicon carbide is then epitaxially grown on the converted surface of the (111) silicon layer. A layer of 2H-gallium nitride then is grown on the epitaxially grown layer of 3C-silicon carbide. The layer of 2H-gallium nitride then is laterally grown to produce the gallium nitride microelectronic layer. The silicon layer is a (111) silicon substrate, the surface of which is converted to 3C-silicon carbide, or the (111) silicon layer is part of a Separation by IMplanted OXygen (SIMOX) silicon substrate which includes a layer of implanted oxygen that defines the (111) layer on the (111) silicon substrate, or the (111) silicon layer is a portion of a Silicon-On-Insulator (SOI) substrate in which a (111) silicon layer is bonded to a substrate.

Methods of fabricating gallium nitride microelectronic layers on silicon layers

Embodiments of the present invention pendeoepitaxially grow sidewalls of posts in an underlying gallium nitride layer that itself is on a sapphire substrate, at high temperatures between about 1000&deg; C. and about 1100&deg; C. and preferably at about 1100&deg; to reduce vertical growth of gallium nitride on the trench floor from interfering with the pendeoepitaxial growth of the gallium nitride sidewalls of the posts. Thus, widely available sapphire substrates may be used for pendeoepitaxial of gallium nitride, to thereby allow reduced cost and/or wider applications for gallium nitride devices. More specifically, gallium nitride semiconductor layers may be fabricated by etching an underlying gallium nitride layer on a sapphire substrate, to define at least one post in the underlying gallium nitride layer and at least one trench in the underlying gallium nitride layer. The at least one post includes a gallium nitride top and a gallium nitride sidewall. The at least one trench includes a trench floor. The gallium nitride sidewalls are laterally grown into the at least one trench, to thereby form a gallium nitride semiconductor layer.

High temperature pendeoepitaxial methods of fabricating gallium nitride semiconductor layers on sapphire substrates

PENDEOEPITAXIAL METHODS OF FABRICATING GALLIUM NITRIDE SEMICONDUCTOR LAYERS ON SILICON CARBIDE SUBSTRATES BY LATERAL GROWTH FROM SIDEWALLS OF MASKED POSTS, AND GALLIUM NITRIDE SEMICONDUCTOR STRUCTURES FABRICATED THEREBY

A sidewall of an underlying gallium nitride layer is laterally grown into a trench in the underlying gallium nitride layer, to thereby form a lateral gallium nitride semiconductor layer. Microelectronic devices may then be formed in the lateral gallium nitride layer. Dislocation defects do not significantly propagate laterally from the sidewall into the trench in the underlying gallium nitride layer, so that the lateral gallium nitride semiconductor layer is relatively defect free. Moreover, the sidewall growth may be accomplished without the need to mask portions of the underlying gallium nitride layer during growth of the lateral gallium nitride layer. The defect density of the lateral gallium nitride semiconductor layer may be further decreased by growing a second gallium nitride semiconductor layer from the lateral gallium nitride layer. In one embodiment, the lateral gallium nitride layer is masked with a mask that includes an array of openings therein. The lateral gallium nitride layer is then grown through the array of openings and onto the mask, to thereby form an overgrown gallium nitride semiconductor layer. In another embodiment, the lateral gallium nitride layer is grown vertically. A plurality of second sidewalls are formed in the vertically grown gallium nitride layer to define a plurality of second trenches. The plurality of second sidewalls of the vertically grown gallium nitride layer are then laterally grown into the plurality of second trenches, to thereby form a second lateral gallium nitride layer. Microelectronic devices are then formed in the gallium nitride semiconductor layer.

Methods of fabricating gallium nitride semiconductor layers by lateral growth from sidewalls into trenches, and gallium nitride semiconductor structures fabricated thereby

A gallium nitride microelectronic layer is fabricated by converting a surface of a (111) silicon layer to 3C-silicon carbide. A layer of 3C-silicon carbide is then epitaxially grown on the converted surface of the (111) silicon layer. A layer of 2H-gallium nitride then is grown on the epitaxially grown layer of 3C-silicon carbide. The layer of 2H-gallium nitride then is laterally grown to produce the gallium nitride microelectronic layer. In one embodiment, the silicon layer is a (111) silicon substrate, the surface of which is converted to 3C-silicon carbide. In another embodiment, the (111) silicon layer is part of a Separation by IMplanted OXygen (SIMOX) silicon substrate which includes a layer of implanted oxygen that defines the (111) layer on the (111) silicon substrate. In yet another embodiment, the (111) silicon layer is a portion of a Silicon-On-Insulator (SOI) substrate in which a (111) silicon layer is bonded to a substrate. Lateral growth of the layer of 2H-gallium nitride may be performed by Epitaxial Lateral Overgrowth (ELO) wherein a mask is formed on the layer of 2H-gallium nitride, the mask including at least one opening that exposes the layer of 2H-gallium nitride. The layer of 2H-gallium nitride then is laterally grown through the at least one opening and onto the mask. A second, offset mask also may be formed on the laterally grown layer of 2H-gallium nitride and a second laterally grown layer of 2H-gallium nitride may be overgrown onto the offset mask. Lateral growth of the layer of 2H-gallium nitride also may be performed using pendeoepitaxial techniques wherein at least one trench and/or post is formed in a layer of 2H-gallium nitride to define at least one sidewall therein. The layer of 2H-gallium nitride is then laterally grown from the at least one sidewall. Pendeoepitaxial lateral growth preferably continues until the laterally grown sidewalls coalesce on the top of the posts or trenches. The top of the posts and/or the trench floors may be masked to promote lateral growth and reduce nucleation and vertical growth.

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Cary, NC, United States of America

Darren B Thomson