Nondestructive measurement of carrier mobility in HEMT epi-structures

We report mercury-probe measurement of the carrier mobility in the two-dimensional electron gas (2DEG) of the epi-structure for GaN-based high electron mobility transistors (HEMTs). This nondestructive method requires no contact metal deposition. The mobility is extracted from the dielectric relaxation frequency of the 2DEG moderated by the barrier layer of the HEMT epi-structure, which is manifested as the inflection frequency of the gate capacitance versus frequency curve. We define the sheet capacitance as the in-plane capacitance of a square thin film to elucidate 2DEG’s large dielectric relaxation frequency and HEMT’s superior high-frequency performance.