Forming enhancement mode III-nitride devices

A method of fabricating a device, comprising:

• providing a second III-N layer on a first III-N layer, the second III-N layer comprising aluminum as a group-III element, the first III-N layer comprising gallium or indium but not aluminum as a group-III element;
• providing an insulator layer on the second III-N layer;
• and
• forming a trench in a first portion of the device, the forming of the trench comprising:
• removing the insulator layer to expose a portion of the second III-N layer in the first portion of the device;
• annealing the device in a gas ambient including oxygen at an elevated temperature to oxidize the exposed portion of the second III-N layer in the first portion of the device;
• and
• removing the oxidized exposed portion of the second III-N layer and exposing a top surface of the first III-N layer in the first portion of the device.

A method of fabricating a nitrogen polar III-N device, comprising:

• providing a III-N material structure comprising a second III-N layer on a first III-N layer, the second III-N layer comprising aluminum as a group-III element, the first III-N layer comprising gallium or indium but not aluminum as a group-III element;
• providing a mask layer on an N-face of the second III-N layer in a second portion of the device but not in a first portion of the device, such that the second III-N layer is exposed in the first portion of the device but not in the second portion of the device;
• annealing the device in a gas ambient including oxygen at an elevated temperature to oxidize the exposed portion of the second III-N layer in the first portion of the device;
• and
• removing the oxidized exposed portion of the second III-N layer in the first portion of the device, thereby exposing a top surface of the first III-N layer in the first portion of the device.

A method for fabricating a III-N device, comprising:

• forming a III-N channel layer on a substrate;
• forming a second III-N barrier layer on the channel layer;
• forming a III-N etch stop layer on the second III-N barrier layer;
• forming a first III-N barrier layer on the III-N etch stop layer;
• forming an insulator layer on the first III-N barrier layer;
• and
• forming a trench in a first portion of the device, the forming of the trench comprising:
• removing the insulator layer in the first portion of the device, wherein a portion of the first III-N barrier layer in the first portion of the device has a thickness away from a top surface of the III-N etch stop layer, the thickness being within a predetermined thickness range;
• annealing the III-N device in a gas ambient including oxygen at an elevated temperature to oxidize the portion of the first III-N barrier layer in the first portion of the device;
• and
• removing the oxidized portion of the first III-N barrier layer in the first portion of the device.

A method of forming a III-N device, comprising:

• forming a III-N channel layer on a substrate;
• forming a III-N barrier layer on the channel layer;
• forming a III-N etch stop layer on the III-N barrier layer;
• forming a p-type III-N layer on the III-N etch stop layer;
• forming a mask layer on the p-type III-N layer in a first portion of the device;
• and
• forming a trench in a second portion of the device, the forming of the trench comprising:
• annealing the III-N device in a gas ambient including oxygen at an elevated temperature to oxidize the p-type III-N layer in the first portion of the device;
• and
• removing the oxidized portion of the p-type III-N layer in the first portion of the device.