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The degradation of transient OFF-state leakage current in AlGaN/GaN HEMTs induced by ON-state gate overdrive was observed and studied. The OFF-state leakage current increases significantly with a pre- ON-state gate overdrive. It takes more than 30 s for the leakage current decay to its equilibrium level in dark. The decay processes follow a stretched-exponential law. We propose that this degradation corresponds to the persistent photoconductivity of GaN buffer induced by the electroluminescence during the Schottky gate overdrive. Both the ON-state gate overdrive bias and duration dependences of the OFF-states leakage degradation were studied. This work indicates that gate-protection is necessary to preserve low OFF-state leakage current and improve device reliability. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

AlN/GaN heterostructures with AlN thin film growing by low-thermal-budget (300 °C) plasma-enhanced atomic layer deposition (ALD) were realized on a semi-insulating GaN-on-sapphire template. By applying in situ ALD-grown Al2O3 as the gate dielectric, thin film transistors (TFTs) have been successfully fabricated. The proposed TFTs exhibit effective gate control with a low subthreshold swing of ∼ 85 mV/dec, an ION/ IOFF ratio of 105 and good channel conductive with a low-field mobility of ∼ 27 cm2/(V·s). This mobility is one order of magnitude higher than that achieved in AlN/GaN heterostructures growing by magnetron sputtering. The enhanced device performance is attributed to a high-quality ALD-AlN/GaN interface obtained by in situ remote-plasma pre-deposition cleaning and the single crystal nature of subsequent epitaxial AlN thin film by plasma-enhanced ALD. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

The GaN-to-Si vertical conduction mechanisms on a low resistivity p-type (111) Si substrate under high-voltage operation are investigated using the temperature-dependent high-voltage C-V characterization and device simulation. It is found the deep depletion and weak inversion in Si will result in a high electric field at the GaN/Si interface and induce the impact ionization of Si. The generated electrons will be injected into GaN buffer layer, fill in buffer traps and act as free carriers in GaN, eventually leading to considerable vertical leakage in the AlGaN/GaN-on-Si structures. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]