The thermal stability performance of double delta-doped In0.42Al0.58As/In0.46Ga0.54As metamorphic heterostructure field-effect transistors with Au and Ti/Au metal gates are comprehensively studied and demonstrated. By evaporating the Ti/Au metal gate, the thermal stability of device characteristics are significantly improved as compared with the device with conventional metal gate (Au). Experimentally, the device with a Ti/Au metal gate simultaneously exhibits the considerably lower temperature degradation in turn-on voltage (-2.19 mV/K), breakdown voltage (-34 mV/K), logic swing (-1.24 mV/K), transition region width (0.05 mV/K), on-off current ratio (-3.55 /K), threshold voltage (-0.25 mV/K), impact ionization-induced gate current (1.63 x 10(-3) mu A/mm K), output conductance (1.23 mu S/mm K), and voltage gain (-0.33 /K) as the temperature is increased from 300 to 510 K. Consequently, the studied device with a Ti/Au metal gate is a good candidate for high-speed and high-temperature digital and switching circuit applications. (c) 2007 The Electrochemical Society.