Annealing temperature stability of ir and ni-based ohmic contacts on AlGaN/GaN high electron mobility transistors

Ti∕Al∕Ir∕Au Ohmic contacts on AlGaN∕GaN high electron mobility transistors (HEMTs) show promising electrical performance, with lower specific contact resistance than obtained with the more conventional Ti∕Al∕Ni∕Au metallization. HEMTs with both types of metallization have been measured up to 550°C. We find that the dc performance of devices with Ir-based contacts is significantly better at each temperature up to this maximum value, with higher transconductance (gm), saturated drain-source current (IDSS), and more stable threshold voltage (Vth). These contacts look very promising for HEMT power amplifier applications involving high temperature operation.

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