Nitride-based transistors having laterally grown active region and methods of fabricating same

A high electron mobility transistor, comprising:

• a semiconductor layer defining a trench therein;
• and
• a group III-nitride layer on the semiconductor layer, the group III-nitride layer having laterally grown portions that are cantilevered over the trench defining a cavity in the trench between the cantilevered laterally grown portions of the group III-nitride layer and a floor of the trench,
• wherein the group III-nitride layer further includes vertically grown portions;
• wherein the laterally grown portions extend from the vertically grown portions and begin above sidewalls of the trench;
• and
• wherein the trench is oriented with respect to a crystal structure to provide one of a vertical sidewall growth of the laterally grown portions of the group III-nitride layer and trapezoidal sidewall growth of the laterally grown portions of the group III-nitride layer,
• wherein the group III-nitride layer further includes a coalescence region between adjacent laterally grown regions, the transistor further comprising:
• a group III-nitride channel layer on the group III-nitride layer;
• a group III-nitride barrier layer on the group III-nitride channel layer;
• a drain contact on the barrier layer;
• a source contact on the barrier layer;
• a gate contact on the barrier layer, wherein the gate contact is disposed on a portion of the barrier layer on a laterally grown region of the group III-nitride layer and at least a portion of one of the source contact and/or the drain contact is disposed on a portion of the barrier layer on a vertically grown region of the group III-nitride layer.