Threshold voltage drift of InP n-channel enhancement mode metal-insulator-semiconductor field-effect transistors

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Abstract
The drift of drain‐to‐source current in enhancement mode InP‐based metal‐insulator‐semiconductor field‐effect transistors is analyzed. We simultaneously measure the time dependence of both the drain‐to‐source current (IDS) and the transconductance of these devices when operated in the saturation regime. From the comparison of these long‐term data, we conclude that the observed drift is caused by a variation in threshold voltage (VT), whereas the carrier mobility in the channel appears to be independent of time. We interpret these results in terms of charge trapping in the gate insulator and infer a slow surface state density of ≳1×1011/cm2. In spite of this relatively low density of states, large scale drifts in VT and IDS are observed. Apparently, this is the first report of the long‐term time dependence of the saturation transconductance and its correlation with IDS drift.