Vertical gallium nitride schottky diode

Abstract

A vertical Schottky diode includes an ohmic contact, a first epitaxial N-type gallium nitride layer physically contacting the ohmic contact and having a first doping concentration, and a second epitaxial N-type gallium nitride layer physically contacting the first epitaxial N-type gallium nitride layer and having a second doping concentration that is lower than the first doping concentration. The vertical Schottky diode further includes a first edge termination region and a second edge termination region coupled to the second epitaxial N-type gallium nitride layer and separated from each other by a portion of the second epitaxial N-type gallium nitride layer, and a Schottky contact coupled to the portion of the second epitaxial N-type gallium nitride layer, and to the first edge termination region and the second edge termination region.

What is claimed is: 
     
         1 . A vertical Schottky diode comprising:
 an ohmic contact;   a first epitaxial N-type gallium nitride layer physically contacting the ohmic contact and having a first doping concentration;   a second epitaxial N-type gallium nitride layer physically contacting the first epitaxial N-type gallium nitride layer and having a second doping concentration that is lower than the first doping concentration;   a first edge termination region and a second edge termination region coupled to the second epitaxial N-type gallium nitride layer and separated from each other by a portion of the second epitaxial N-type gallium nitride layer; and   a Schottky contact coupled to the portion of the second epitaxial N-type gallium nitride layer, and to the first edge termination region and the second edge termination region.   
     
     
         2 . The vertical Schottky diode of  claim 1  further comprising a metal tab attached to the ohmic contact via a solder. 
     
     
         3 . The vertical Schottky diode of  claim 1  wherein the second epitaxial N-type gallium nitride layer has a thickness ranging from about 10 μm to about 25 μm. 
     
     
         4 . The vertical Schottky diode of  claim 1  wherein the second epitaxial N-type gallium nitride layer comprises an epitaxial interfacial layer at an interface with the first epitaxial N-type gallium nitride layer. 
     
     
         5 . The vertical Schottky diode of  claim 1  wherein the first doping concentration ranges from about 1×10 18  cm −3  to about 5×10 18  cm −3 . 
     
     
         6 . The vertical Schottky diode of  claim 5  wherein the second doping concentration ranges from about 2×10 15  cm −3  to about 1×10 16  cm −3 . 
     
     
         7 . The vertical Schottky diode of  claim 1  wherein each of the first edge termination region and the second edge termination region comprises gallium nitride doped with magnesium (Mg). 
     
     
         8 . The vertical Schottky diode of  claim 1  further comprising a plurality of junction barrier Schottky (JBS) grid regions in the portion of the second epitaxial N-type gallium nitride layer between the first edge termination region and the second edge termination region, the plurality of JBS grid regions being coupled to the Schottky contact. 
     
     
         9 . The vertical Schottky diode of  claim 8  wherein each of the plurality of JBS grid regions comprises gallium nitride doped with magnesium (Mg). 
     
     
         10 . The vertical Schottky diode of  claim 1  wherein each of the first edge termination region and the second edge termination region comprises a single zone having a third doping concentration ranging from about 2×10 15  cm −3  to about 5×10 16  cm −3 . 
     
     
         11 . The vertical Schottky diode of  claim 1  wherein each of the first edge termination region and the second edge termination region comprises a first zone and a second zone, the first zone having a third doping concentration ranging from about 2×10 15  cm −3  to about 5×10 16  cm −3 , and the second zone having a fourth doping concentration ranging from about 5×10 16  cm −3  to about 5×10 17  cm −3 . 
     
     
         12 . A vertical Schottky diode comprising:
 a metal tab;   an ohmic contact coupled to the metal tab;   a first epitaxial N-type gallium nitride layer electrically contacting the ohmic contact and having a first doping concentration;   a second epitaxial N-type gallium nitride layer physically contacting the first epitaxial N-type gallium nitride layer and having a second doping concentration that is lower than the first doping concentration; and   a Schottky contact coupled to a portion of the second epitaxial N-type gallium nitride layer, the Schottky contact having a step-wise structure such that a cross-section of the Schottky contact is narrower in a region proximal to the second epitaxial N-type gallium nitride layer and wider in a second region distal to the second epitaxial N-type gallium nitride layer.   
     
     
         13 . The vertical Schottky diode of  claim 12  wherein the second epitaxial N-type gallium nitride layer has a thickness ranging from about 10 μm to about 25 μm. 
     
     
         14 . The vertical Schottky diode of  claim 12  wherein the first doping concentration ranges from about 1×10 18  to about 5×10 18 . 
     
     
         15 . The vertical Schottky diode of  claim 14  wherein the second doping concentration ranges from about 2×10 15  to about 1×10 16 .