The objective of this paper is to investigate and explore the potential of AlGaN/GaN based metal insulator semiconductor heterostructure field effect transistor (MISHFET) device for high temperature applications. A temperature dependent analytical model is proposed taking into account the effect of various temperature dependent material properties. The electrical characteristics like drain current, transconductance, cut-off frequency and saturation output power are evaluated for temperature range up to 573 K and a relative comparison is done with conventional HFET structures.