
50 Gallium Nitride (GaN): Physics, Devices, and Technology
2.6 EVALUATION OF TRANSISTORS
To evaluate the potentialities of these structures, test devices including transmission
line model (TLM) and isolation patterns, diodes, and transistors have been fabricated
by photolithography. The device process starts with mesa denition by reactive ion
etching (RIE) step in a Cl
2
/Ar/CH
4
mixture. After a short RIE etching, TiAlNiAu
stacks are deposited by e-beam evaporation. The ohmic contacts are achieved after
rapid thermal annealing at 750°C for 30 seconds. NiAu lms are then evaporated for
gate Schottky contact as well as for access pads. These devices ...