Contacts consisting of various single layer metals to n-type GaN have been formed and characterized. The current-voltage characteristics were measured for 17 different metals (Sc, Hf, Zr, Ag, Al, V, Nb, Ti, Cr, W, Mo, Cu, Co, Au, Pd, Ni, and Pt) deposited on the same epitaxial growth layer. The barrier height, ideality factor, breakdown voltage, and effective Richardson coefficients were measured from those metals which exhibited strong rectifying behavior. The barrier heights for these metal contacts were measured using current-voltagetemperature and capacitance-voltage techniques. It was found that an increase in metal work function correlated with an increase in the barrier height. The surface state density of GaN was approximated to be very similar to CdS and almost a factor of ten less than GaAs.

Schottky barriers of Ti, Cr, Au, Pd, Ni and Pt on n-type GaN epitaxial layers grown by low-pressure metal-organic chemical vapour deposition on sapphire have been fabricated and characterized. Measurements were carried out using current-voltage (I -V ), current-voltage-temperature (I -V -T ) and capacitance-voltage (C -V ) techniques. A modified Norde plot was used as one of the analysis tools for the I -V -T measurements. The barrier heights, ideality factors and effective Richardson constants are presented. Barrier heights of 0.88, 0.92, 0.99 and 1.08 eV for Au, Pd, Ni and Pt respectively were obtained from the modified Norde plot. Contacts of Ti and Cr exhibited only slightly rectifying characteristics. These results show that the barrier height on n-GaN increases monotonically, but does not scale proportionately, with increasing metal workfunction.

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Dry etch-induced damage has been investigated using Pd Schottky diodes fabricated on n-type GaN surfaces that were etched by reactive ion etching in SiC14 and Ar plasmas. Damage was evaluated by measuring the current-voltage, current-voltage-temperature, and capacitance-voltage characteristics of the diodes. A plasma chemistry that includes a chemical etching component (SiCl 4) was found to significantly reduce the degree of induced damage in comparison to a chemistry that uses only a physical component (Ar). The effective barrier height, ideality factor, reverse breakdown voltage, reverse leakage current, and the effective Richardson coefficient of diodes etched under various plasma conditions are presented. The degree of etch-induced damage was found to depend strongly on the plasma self-bias voltage but saturates with etch time after an initial two-minute etch period. Rapid thermal annealing was found to be effective in improving the diode characteristics of the etched GaN samples.

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