Extraction of transport dynamics in AlGaN/GaN HFETs through free carrier absorption

The importance of AlGaN/GaN heterostructure field-effect transistor (HFETs) in high-power high-frequency applications is now well established. However, detailed information on high-field mobilities, velocity-field relations, carrier temperature, and momentum and energy relaxation times are not available. In this paper we carry out theoretical simulations based on Monte Carlo techniques to show that transport dynamics can be effectively extracted through free carrier absorption. Using short pulses of infrared radiation, it is possible to obtain the velocity-field curve by fitting the absorption spectrum without heating the device. We show this by solving the classical transport equation and then verify the results through Monte Carlo simulations. With the model presented it would be possible to extract carrier dynamics from experimentally measured results. Our work suggests that free carrier absorption experiments on AlGaN/GaN HFETs would provide important transport information, which would be very useful in device design and modeling.