Patent ID: 8513703

Claim:
A method of forming a transistor comprising: forming a multi-layered substrate structure having a first layer of p-type material, having a first doping level and a second layer of n-type material, having a lightly doped bottom portion and a heavily doped top portion, that touches a top surface of the first layer, wherein the lightly doped portion of the second layer is lighter doping than the first doping level, wherein the first layer is substantially thicker than the second layer, the multi-layered substrate structure having a top surface, the first layer and the second layer of the multi-layered substrate structure forming a p-n junction therebetween; forming a buffer layer to touch the top surface of the multi-layered substrate structure, no portion of the buffer layer touching the first layer, the buffer layer having a top surface and including a group III-nitride, wherein the n-type second layer is configured to be thick enough and have enough doping to prevent the buffer layer from forming a p-type region in the n-type second layer, which extends through the n-type second layer, thereby shorting the p-n junction formed by the n-type second layer and the p-type first layer; forming a channel layer to touch the top surface of the buffer layer, the channel layer including a group III-nitride and having a top surface; forming a barrier layer to touch the top surface of the channel layer, the barrier layer including a group III-nitride; forming spaced-apart metal source and drain regions that contact the channel layer; and forming a beveled edge that extends from the top surface of the barrier layer to the bottom surface of the multi-layer substrate structure, the beveled edge being formed by removing a larger amount of the more lightly doped side of the p-n junction than it does from the more heavily doped side of the p-n junction resulting in a beveled edge that is wider at the top of the die than at the bottom of the die, known as a positive bevel angle, the positive bevel resulting in removing a larger amount from the more lightly doped second layer to cause the depletion region to curve upward, becoming much wider at the beveled edge, wherein the increased width of the depletion region, substantially increasing the junction breakdown voltage at the edge of the bevel.