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Influence of surface states on the voltage robustness of AlGaN/GaN HFET power devices

: Wespel, M.; Dammann, M.; Baeumler, M.; Polyakov, V.M.; Reiner, R.; Waltereit, P.; Quay, R.; Mikulla, M.; Ambacher, O.

JEDEC, Arlington/Va.:
29th Annual JEDEC ROCS Workshop 2014 : Proceedings, 19 May 2014, Denver, Colorado
Arlington/Va.: JEDEC, 2014
Reliability of Compound Semiconductors Workshop (ROCS) <29, 2014, Denver/Colo.>
Conference Paper
Fraunhofer IAF ()
reliability; breakdown voltage; leakage current; AlGaN/GaN-on-SiC; interface charge; HTRB; capacitance-voltage test; electroluminescence; field plate design

In this work we discuss the influence of the donor-like surface state density (SSD) on leakage currents and the breakdown voltages of AlGaN/GaN heterostructure field-effect transistors (HFET) at high temperature reverse bias (HTRB) step stress. A method to extract charges at the surface by high voltage capacitance voltage (HV-CV) profiling of the gate-drain diode of a HFET is presented. The SSD of the first sample is found to be similar to the polarization charge whereas it is elevated by a factor of three on the second sample. The sample with the higher SSD has severe deficiencies in robustness found in the HTRB. The stress data, the simulation model and the images of electroluminescence (EL) indicate that at catastrophic failure arises underneath the gate field plate (GFP).