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The temperature-dependent electrical characteristics of Schottky rectifiers fabricated with a SiO2 field plate on a freestanding n- gallium nitride (GaN) substrate were reported in the temperature range of 298–473 K. The Schottky barrier heights evaluated from forward current-voltage measurement revealed an increase of Schottky barrier height and series resistance but a decrease of ideality factor (n) with increasing temperature. However, the Schottky barrier heights evaluated from capacitance-voltage measurement remained almost the same throughout the temperature range measured. The Richardson constant extrapolated from ln(J0/T2) vs 1/T plot was found to be 0.029 A cm-2 K-2. A modified Richardson plot with ln(J0/T2) vs 1/nT showed better linearity, and the corresponding effective Richardson constant was 35 A cm-2 K-2. The device showed a high reverse breakdown voltage of 560 V at room temperature. The negative temperature coefficients were found for reverse breakdown voltage, which is indicative of a defect-assisted breakdown. [ABSTRACT FROM AUTHOR]

The authors present the fabrication and characterization of vertical-geometry Schottky-type ultraviolet (UV) photodetectors based on a bulk n-GaN substrate. By using low temperature rapid thermal annealing of the semitransparent Schottky contacts (nickel with 7% vanadium), they obtained an ultralow dark current of 0.56 pA at -10 V reverse bias. A responsivity of ∼0.09 A/W at zero bias was measured for wavelength shorter than the absorption edge of GaN, and it was found to be independent of the incident power in the range measured (50 mW/m2–2.2 kW/m2). The devices are visible blind, with an UV/visible contrast of over six orders of magnitude. An open-circuit voltage of 0.3 V was also obtained under a broadband UV illumination. [ABSTRACT FROM AUTHOR]

A vertical Schottky diode rectifier was fabricated using a bulk n-GaN wafer. Pt Schottky contacts were prepared on the Ga face and full backside ohmic contact was prepared on the N face by using Ti/Al. The root mean square surface roughnesses of the Ga and N faces are 0.61 and 4.7 nm, respectively. A relatively high breakdown field of 5.46 kV/cm was achieved with no additional edge termination. The breakdown field decreases as the size of the device increases. The background electron concentration of the bulk GaN wafer was low (5×1015 cm-3), which may lead to a relatively high breakdown field even with no special edge termination. The forward turn-on voltage was as low as 2.4 V at the current density of 100 A/cm2. The device exhibited an ultrafast reverse recovery characteristics (reverse recovery time <20 ns). [ABSTRACT FROM AUTHOR]