Performances and reliability of HEMTs: State of the art and experimental analysis

In recent years, high electron mobility transistors (HEMTs) have become commercially available, offering extremely interesting performances when high operating frequencies and low noise are required. Consequently, increasing attention has been paid to their reliability with a number of accelerated life tests carried out in many different laboratories all over the world. The first part of this paper attempts to give a review of the principles of functioning and of the reliability studies on these transistors, while the second part presents the data obtained in CSELT laboratories from reliability storage tests at 200°C and at 300°C carried out on HEMTs samples from four different manufacturers. At different times, tests were interrupted and the most important electrical characteristics such as saturation current, drain source and transconductance were measured. The variations of measured parameters during storage tests are discussed with the results of the failure analysis in order to understand the failure mechanisms.