Simulation of Deep-Level Trap Distributions in AlGaN/GaN HEMTs and Its Influence on Transient Analysis of Drain Current

Abstract

AlGaN/GaN high electron mobility transistors for high efficiency power switching applications are susceptible to charge trapping by deep-levels in the GaN buffer resulting in current collapse during gate and drain voltage swings. Although drain-current transient based methodologies have been used consistently to extract trap parameters, the factors affecting the non-exponential nature of the transient are still not well understood. No effort at accurately replicating multiple deep-levels in the GaN buffer to simulate transient response of GaN based power devices has been reported previously. In this work, we present numerical simulation results of HEMTs having multiple discrete trap states as well as band-like distribution of traps in the GaN band-gap. On-state current of synchronous gate and drain pulsing simulations show current as a sum of stretched multiexponentials, with stretching factor showing trap and Fermi-level dependence. Using this capability incorporated into FLOODS TCAD simulator and definition of deep-levels in the GaN buffer precisely, modeling of non-exponential transients and associated wide peaks in the transient derivatives can be carried out accurately.