An AlGaAs/InGaAs/GaAs pseudomorphic high electron mobility transistor (pHEMT) with double delta-doping carrier supply layers was fabricated and characterized. Estimates of typical device characteristics (extrinsic transconductance (g(m)), drain current density (I-D), threshold voltage (V-th), current gain cut-off frequency (f(T)), maximum frequency of oscillation (f(max)), noise behavior, and large signal measurements) were made. A series of experiments was conducted to assess the effects of temperature on pHEMT. A peak g(m) of 161 mS/mm was obtained from the fabricated pHEMT with a gate length of 1 mu m for room-temperature operation. The transistor characteristics showed evidence of high breakdown voltages. With respect to the variation in two-terminal gate-drain breakdown voltage, this device had a positive temperature coefficient from 300 to 450 K, and a negative temperature coefficient at temperatures surpassing 450 K. Strikingly, high-frequency on-wafer measurements on the fabricated pHEMT were made up to 400 K, revealing nearly no change in f(T). Not only was the device characterized and the complicated mechanisms at various temperatures elucidated, but also the favorable potential of the presented pHEMT for high-temperature and high-frequency applications was determined. (c) 2007 The Electrochemical Society.