Schottky Barrier Parameters and Low-Frequency Noise Characteristics of Au/Ni Contact to n-Type β-Ga₂O₃

An Au/Ni/β-Ga₂O₃ Schottky barrier diode was fabricated on an 8.6-μm-thick lightly doped drift region grown on heavily doped Ga₂O₃ substrate, and its electrical and low-frequency noise characteristics were investigated. The diode showed excellent rectifying behavior with the reverse current being saturated with the applied bias and a magnitude of ∼ 10⁻¹³ A. The diode exhibited a barrier height of 1.04 eV and a reasonably high reverse breakdown voltage of 540 V without employing any edge termination methods. The Schottky barrier parameters, such as barrier height, ideality factor, and series resistance, were obtained using a range of methods and found to be in close agreement with each other. The interface state density of the Au/Ni/β-Ga₂O₃ Schottky diode obtained from the capacitance–voltage (C–V) method was lower than that determined from the forward current–voltage (I–V) characteristics, attributed to the inhomogeneous distribution of interface states at the interface. An analysis of the forward log I–log V plot of the Au/Ni/β-Ga₂O₃ Schottky diode revealed ohmic-type conduction, and space-charge-limited current dominated the carrier transport mechanisms in lower and higher voltage ranges, respectively. For bias below 0.3 V, the low-frequency noise of the Au/Ni/β-Ga₂O₃ Schottky diode was a linear combination of two noise components associated with uniformly distributed bulk traps of β-Ga₂O₃ and the charge fluctuation in the generation-recombination center. On the other hand, for bias above 0.4 eV, the noise spectral density showed a 1/f² dependence, indicating the domination of generation-recombination noise.