Unified Mechanism for Positive- and Negative-Bias Temperature Instability in GaN MOSFETs

• Published in: IEEE transactions on electron devices Vol. 64; no. 5; pp. 2142 - 2147
• Main Authors: Guo, Alex, del Alamo, Jesus A.
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.05.2017; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Bias; Bias temperature instability (BTI); Conduction bands; Electron traps; Evolution; Fermi surfaces; Gallium nitride; gallium nitride MOSFETs; Gallium nitrides; Logic gates; MOSFET; MOSFETs; Negative bias temperature instability; oxide trapping; Room temperature; semiconductor device reliability; Stress; Temperature dependence; Thermal variables control; Threshold voltage; Time dependence; Transconductance
• ISSN: 0018-9383; 1557-9646
• DOI: 10.1109/TED.2017.2686840

We present a comprehensive study of bias temperature instability (BTI) in GaN MOSFETs under moderate positive and negative gate bias stress. We investigate the evolution of threshold voltage (V T ), maximum transconductance (g m,max ), and subthreshold swing (S). Our results show a universal continuous, symmetrical, and reversible VT shift and gm,max change as gate stress voltage (VGS,stress) increases from -5 to 5V at room temperature. The time evolution of V T is well described by a power law model. The voltage dependence, time dependence, and temperature dependence of our results suggest that for moderate gate bias stress, positive BTI and negative BTI are due to a single reversible mechanism. This is electron trapping/detrapping in preexisting oxide traps that form a defect band very close to the GaN/oxide interface and extend in energy beyond the conduction band edge of GaN and below the Fermi level at the channel surface at 0 V.