Formation of Ohmic contacts in AlGaN/GaN HEMT structures at 500 °C by Ohmic contact recess etching

Good Ti/Al/Ti/Au Ohmic contacts were achieved in undoped-AlGaN/GaN HEMT structures at 500 °C (measured by a thermocouple) by using an Ohmic contact recess etch. The Ohmic recess etch is deeper than the undoped AlGaN layer and hence reaches the two-dimensional electron gas. Good morphology and well-defined edge profile are also achieved. Because of the low temperature, this process can tolerate quite some water vapor related issue during Ohmic contact anneal.