We report on the fabrication and characteristics of AlSb/InAs high electron mobility transistors (HEMTs) with a TiW/Au gate metalization. Using gate leakage and S-parameter measurements as a measure of stability, the HEMTs were found to be thermally stable up to 180 degreesC when heat treated in a H-2/N-2 ambient. (C) 2002 Elsevier Science Ltd. All rights reserved.