Schottky diode with buried layer in gan materials

Abstract

A semiconductor structure includes a III-nitride substrate characterized by a first conductivity type and having a first side and a second side opposing the first side, a III-nitride epitaxial layer of the first conductivity type coupled to the first side of the III-nitride substrate, and a plurality of III-nitride epitaxial structures of a second conductivity type coupled to the III-nitride epitaxial layer. The semiconductor structure further includes a III-nitride epitaxial formation of the first conductivity type coupled to the plurality of III-nitride epitaxial structures, and a metallic structure forming a Schottky contact with the III-nitride epitaxial formation and coupled to at least one of the plurality of III-nitride epitaxial structures.

What is claimed is: 
     
         1 . A method of fabricating a diode in gallium nitride (GaN) materials, the method comprising:
 providing a n-type GaN substrate having a first surface and a second surface;   forming a first n-type GaN epitaxial layer coupled to the first surface of the n-type GaN substrate;   forming a p-type GaN epitaxial layer coupled to the first n-type GaN epitaxial layer;   removing at least a portion of the p-type GaN epitaxial layer to form a plurality of p-type device structures;   forming a second n-type GaN epitaxial layer coupled to the plurality of p-type device structures;   removing at least a portion of the second n-type GaN epitaxial layer to expose a portion of at least one p-type device structure; and   forming a first metallic structure electrically coupled to the exposed portion of the at least one p-type device structure and a remaining portion of the second n-type GaN epitaxial layer, wherein the first metallic structure is formed without prior cleaning and without prior annealing of the at least one p-type device structure and a remaining portion of the second n-type GaN epitaxial layer.   
     
     
         2 . The method of  claim 1  wherein the first metallic structure forms a Schottky contact with the remaining portion of the second n-type GaN epitaxial layer. 
     
     
         3 . The method of  claim 1  wherein the first metallic structure forms an ohmic contact with the exposed portion of the at least one p-type device structure. 
     
     
         4 . The method of  claim 1  wherein forming the plurality of p-type device structures includes forming one or more edge termination structures. 
     
     
         5 . The method of  claim 4  wherein the one or more edge termination structures circumscribe the first metallic structure. 
     
     
         6 . The method of  claim 1  wherein forming the first metallic structure includes forming the first metallic structure such that one or more p-type device structures are disposed between the first n-type GaN epitaxial layer and the first metallic structure. 
     
     
         7 . The method of  claim 1  further comprising forming a second metallic structure electrically coupled to the second surface of the n-type GaN substrate. 
     
     
         8 . The method of  claim 1  wherein:
 the n-type GaN substrate is characterized by a first n-type dopant concentration; and 
 the first n-type GaN epitaxial layer is characterized by a second n-type dopant concentration less than the first n-type dopant concentration. 
 
     
     
         9 . A method of fabricating an epitaxial structure, the method comprising:
 providing a III-nitride substrate of a first conductivity type;   forming a first III-nitride epitaxial layer of the first conductivity type coupled to a first surface of the III-nitride substrate;   forming a second III-nitride epitaxial layer of a second conductivity type coupled to the first III-nitride epitaxial layer;   removing at least a portion of the second III-nitride epitaxial layer to form a plurality of epitaxial structures of the second conductivity type;   forming a third III-nitride epitaxial layer of the first conductivity type coupled to the plurality of epitaxial structures; and   forming a first metallic structure electrically coupled to at least one of the epitaxial structures and to a portion of the third III-nitride epitaxial layer, wherein the first metallic structure is formed without prior cleaning and without prior annealing of the at least one of the epitaxial structures and of the portion of the third III-nitride epitaxial layer.   
     
     
         10 . The method of  claim 9  wherein forming the third III-nitride epitaxial layer comprises a selective regrowth process. 
     
     
         11 . The method of  claim 9  further comprising removing at least a portion of the third III-nitride epitaxial layer. 
     
     
         12 . The method of  claim 9  wherein the first metallic structure is configured to form a Schottky contact with the third III-nitride epitaxial layer. 
     
     
         13 . The method of  claim 9  wherein the first metallic structure forms an ohmic contact with the at least one of the plurality of epitaxial structures. 
     
     
         14 . The method of  claim 9  wherein forming the plurality of epitaxial structures includes forming one or more edge termination structures. 
     
     
         15 . The method of  claim 9  wherein forming the first metallic structure includes forming the first metallic structure such that one or more epitaxial structures are disposed between the first III-nitride epitaxial layer and the first metallic structure. 
     
     
         16 . The method of  claim 9  further comprising forming a second metallic structure electrically coupled to a second surface of the III-nitride substrate. 
     
     
         17 . The method of  claim 9  wherein the first conductivity type is n-type and the second conductivity type is p-type.