Cellular automaton approach for carrier degeneracy effects on the electron mobility of high electron mobility transistors (HEMT's)

GaN-based high electron mobility transistors (HEMTs) are expected to have high performance in base station applications. Recently, it was reported that the combination of the Poisson-Schrodinger method and cellular automaton method is effective for predicting the mobility of channel two-dimensional electron gas (2DEG) of GaN HEMTs. In the operation condition of HEMT, the surface electron density of the channel is on the order of 1013 cm-2, and the effect of degeneracy cannot be ignored in calculating the mobility. Since the electron distribution function is always stably obtained by the cellular automaton method, the degeneracy effect can be considered stably. In this paper, through the comparison of different degeneracy evaluation methods, the anisotropy of the electron distribution function under the electric field acceleration is clarified to affect the HEMT mobility prediction significantly.