Surface voltage response to pulses of piezoelectric polarization is measured with a Kelvin-probe providing a unique means for investigation of the dynamics of polarization induced sheet charge and 2DEG. Combined with biasing of the surface with a corona-deposited charge from accumulation to deep depletion and corresponding non-contact C-V type characterization, the technique identifies surface band bending and interface traps as key factors that affect the magnitude and time decay of piezoelectric polarization. For 2DEG structures, surface potential pinning is observed when the 2DEG is fully populated. Pinning is released by negative corona charging to fully deplete the 2DEG. These results are consistent with the role of surface states. Presently demonstrated polarization modulation and wafer scale measurements shall impact the in-depth characterization and fundamental understanding of AlGaN/GaN 2DEG structures.
Marshall Wilson, Bret Schrayer, Alexandre Savtchouk, Bob Hillard, and Jacek Lagowski, "Piezoelectric modulation of surface voltage in GaN and AlGaN/GaN: charge screening effects and 2DEG," Proc. SPIE 10104, Gallium Nitride Materials and Devices XII, 101041E (Presented at SPIE OPTO: February 01, 2017; Published: 16 February 2017); https://doi.org/10.1117/12.2249593.
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