High electron mobility transistor and method of forming the same

A high electron mobility transistor (HEMT) comprising:

• a gallium nitride (GaN) layer on a substrate;
• an aluminum gallium nitride (AlGaN) layer on the GaN layer;
• a salicide source feature and a salicide drain feature spaced apart and on the AlGaN layer, wherein each of the salicide source feature and the salicide drain feature has a concave surface;
• and
• a gate electrode over a portion of the AlGaN layer between the salicide source feature and the salicide drain feature.

A high electron mobility transistor (HEMT) comprising:

• a channel layer;
• a donor-supply layer on the channel layer and different from the channel layer in composition;
• a salicide source feature and a salicide drain feature in contact with the channel layer through the donor-supply layer;
• a gate electrode over a portion of the donor-supply layer between the salicide source feature and the salicide drain feature;
• and
• a carrier depletion layer between the gate electrode and the donor-supply layer, wherein the carrier depletion layer contains point defects.