Original Publication Date
Applied Physics Letters
DOI of Original Publication
Date of Submission
This work investigates the correlation between surfacecharging and current collapse in an AlGaN∕GaNheterostructurefield effect transistor.Surfacecharging due to applied biases was sensed by mapping the surface potential between the gate and drain using scanning Kelvin probe microscopy. Due to the bias, the surface band bending near the gate edge was observed to increase by as much as 1 eV. This increase of band bending is caused by an accumulation of excess charge near the surface during the applied bias. By varying the duration of the applied bias, we find that this accumulation of excess charge near the gate takes about 20 s to saturate. Continuous monitoring of the surface potential after switching off the bias shows that a complete relaxation of the excess band bending requires about 800 s. Drain current transient measurements show that the collapse and recovery of the drain current also occur on similar time scales. This correlation between time scales indicates that the accumulation of excess charge near the gate edge causes current collapse by depletion of the channel.
Sabuktagin, S., Doğan, S., Baski, A.A., et al. Surface charging and current collapse in an AlGaN∕GaN heterostructure field effect transistor. Applied Physics Letters, 86, 083506 (2005). Copyright © 2005 AIP Publishing LLC.
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VCU Electrical and Computer Engineering Publications