Enhanced electrical performance of Au/n-GaN Schottky diodes by novel processing

Au/n-GaN Schottky diodes with the Au electrode deposited at low temperature (LT) (77 K) and at room temperature were compared. Photoluminescence and x-ray rocking curve measurements were performed prior to device fabrication. The best LT Schottky diodes exhibited excellent performances with leakage current densities as low at 2.55 x 10(-11) A cm(-2) at -2.5 V. By using the commonly used;effective Richardson constant value, typical zero-biased barrier heights of Phi(B0) = 1.08 eV and zero electric field barrier heights of Phi(BF) = 1.32 eV we obtained, with the best values of Phi(B0) = 1.22 eV, Phi(BF) = 1.88 eV for the LT diode. A possible model to interpret this high barrier height was proposed. It was found that great differences existed between the saturated reverse current and that extrapolated from the linear region of the forward I-V curve. A deep state-assisted tunnel mechanism was proposed to qualitatively explain this feature for diodes with low leakage currents. The obvious enhancement in electrical performance makes LT processing a very promising technique for GaN device application although details of the conduction mechanism for LT Au/ n-GaN Schottky diodes are still under investigation. (C) 1999 American Vacuum Society. [S0734-2101(99)16704-6].