Characterizing drain current dispersion in GaN HEMTs with a new trap model

Dispersion in a GaN HEMT, including gate and drain lag, is related to a new trapping model based on SRH theory. The model is used to explain the bias- and terminal-potential dependency of the turn-on transients and their time constants. Because the time constants are extremely long they impact the measurement of true dc characteristics and contribute to knee walk-out. Temperature as a function of time is shown to be a vital consideration. The models of both drain current and trapping need to consider temperature and power dissipation versus time. The relationship between trap potentials and terminal potentials is investigated.