Comparison of optoelectrical characteristics between Schottky and Ohmic contacts to β-Ga2O3 thin film

Schottky and Ohmic contacts are key matters affecting carrier transport in oxide semiconductor-based electrical and optical devices. For Ga2O3, the comparison of optoelectrical behaviors and the fundamental physical mechanism between these two contacts are not well known yet. In this work, beta-Ga2O3 thin films were grown via metal-organic chemical vapor deposition then deposited with symmetrical Ni/Au (Schottky) or Ti/Au (Ohmic) contacts. Optoelectrical measurements show that the Ohmic contacted device exhibits superior responsivities thanks to its higher photocurrents. Meanwhile, for the Schottky contacted device, firstly, it has a faster response speed, and secondly it exhibits larger photo-to-dark current ratios owing to their low dark current. Specifically, the voltage- and light intensity-dependent responsivity and detectivities of the Schottky and Ohmic contacted devices were measured and discussed under the consideration of different voltages and UV light intensities.