Carrier Transport and Gain Mechanisms in β-Ga2O3-Based Metal-Semiconductor-Metal Solar-Blind Schottky Photodetectors

In this paper, carrier transport and gain mechanisms are exploited in the beta-Ga2O3-based metal-semiconductor-metal photodetectors with Au back-to-back Schottky contacts. The resultant devices exhibit a low dark current of < 10 pA at 10 V, a sustaining bias over 500 V without electric breakdown, a self-powered sensitivity with a UVC-to-visible rejection ratio over 10(3), and a photo-to-dark current ratio of 50 at 473 K, indicative of its strong operation capability at high temperature and in harsh environments. Temperature-dependentcurrent-voltage-features reveal that the dark reverse leakage is dominated by the thermionic field emission at low electric field and Poole-Frenkel emission from a deep trap level of 0.42 eV under the conduction band at high field, respectively. These negatively charged traps positioned below the Fermi level in the vicinity of Schottky interface capture photogenerated holes and reduce the barrier height upon illumination. The temperature- and bias-dependent photoresponse features are identified in physics that the photoconductive gain as well as slow response speed is originated from the change of barrier height due to trap repopulation.