Distribution of trap energy level in AlGaN/GaN high-electron-mobility transistors on Si under ON-state stress.

The distribution of trap energy (DTE) levels was observed in the energy band gap of buffer GaN by temperature-dependent current transient measurements on AlGaN/GaN HEMTs under fully ON drain-stress (V_{D[ON]_Stress}) conditions. The activation energies (E_a’s) obtained from current transients increase with increasing V_{D[ON]_Stress}. Using a multitrap energy (MTE) model, the applied-V_{D[ON]_Stress}-dependent E_a is attributed to DTE levels in the GaN energy band gap, rather than to discrete single trap energy levels. An effective activation energy (E_{a_eff}) corresponding to trap energy levels activated by the applied V_{D[ON]_Stress} is thus obtained. This observation is validated with two-dimensional numerical simulations. This study will help device designers develop a “DTE-dependent” emission time constant model that is readily applicable for the reliability modelling of future GaN-based circuits. [ABSTRACT FROM AUTHOR]