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Publication - Professor Martin Kuball

    'Kink' in AlGaN/GaN-HEMTs

    Floating buffer model

    Citation

    Singh, M, Uren, M, Martin, T, Karboyan, S, Chandrasekar, H & Kuball, M, 2018, ‘'Kink' in AlGaN/GaN-HEMTs: Floating buffer model’. IEEE Transactions on Electron Devices, vol 65., pp. 3746-3753

    Abstract

    We report on a floating buffer model to explain 'kink,' a hysteresis in the output characteristics of Fe-doped AlGaN/GaN HEMTs observed at low drain bias. Unintentionally doped background carbon can make the GaN buffer p-type allowing it to electrically float. We further note that reverse bias trap-assisted leakage across the junction between the 2DEG and the p-type buffer can provide a mechanism for hole injection and buffer discharging at just a few volts above the knee, explaining the 'kink' bias dependence and hysteresis. We show that HEMTs with a different background carbon have dramatically different kink behaviors consistent with the model. Positive and negative magnitude drain current transient signals with 0.9-eV activation energy are seen, corresponding to changes in the occupation of carbon acceptors located in different regions of the GaN buffer. The observation of such signals from a single trap calls into question conventional interpretations of these transients based on the bulk 1-D deep-level transient spectroscopy (DLTS) models for GaN devices with floating regions.

    Full details in the University publications repository