Properties of Ir-based Ohmic contacts to AlGaN/GaN high electron mobility transistors

Measurement of the electrical characteristics of 250 devices on the same 2 in. diameter wafer shows that Ti/Al/Ir/Au Ohmic contacts on AlGaN/GaN high electron mobility transistors (HEMTs) have lower average specific contact resistance after annealing at 850degreesC for 30 s (4.6x10(-5) Omega cm(2)) compared to more standard Ti/Al/Ni/Au contacts (2x10(-4) Omega cm(2)). HEMTs with these Ir-based contacts also show average interdevice isolation currents approximately a factor of 2 lower, higher peak transconductance (134 mS/mm compared to 121 mS/mm), and higher device breakdown voltage (31 V compared to 23 V) than the devices with Ni-based contacts. This Ir-based contact metallurgy looks promising for applications requiring extended thermal stability of the HEMTs. (C) 2004 American Institute of Physics.