The temperature-dependent characteristics of the non-annealed Ohmic contacts InAlAs/InGaAs MHEMT are studied and demonstrated. Due to the use of Ohmic-recess technique, the improvements on device performance including higher saturation drain current, higher transconductance, lower on-resistance, lower parasitic resistance, more linear operating regime, and superior microwave performance are obtained. The non-annealed Ohmic contacts device also shows good properties at higher operating temperature regime and the relatively thermal stable performance over the operating temperature range (300-500 K). Therefore, the studied device with non-annealed Ohmic contacts process provides the promise for high-temperature and high-performance microwave electronic device applications. (C) 2009 Elsevier Ltd. All rights reserved.