Fabrication of Si/ZnO Vertical N–n+ and P–p+ Isotype Junction Devices by Pulsed Laser Deposition

Device development and electrical characterization of high quality zinc oxide (ZnO) thin films grown on silicon (100) substrates are presented in this paper. Thin films of ZnO are grown at an optimized growth temperature of 300°C and two oxygen overpressure regimes on n and p-type Si substrates by pulsed laser deposition technique. Current–voltage characteristics of four devices are investigated by deposition of silver contacts on ZnO films and back gating the substrates. Rectifying properties are observed for two devices: one, for the n-Si substrate device with the film grown at low (6.66×10−4Pa) oxygen overpressure and two, for the p-Si device with ZnO grown at high (3.33×10−2Pa) oxygen. For the other two devices, namely the devices with the films grown on n-Si at high oxygen and p-Si at low oxygen pressure less pronounced rectifications are observed. Forward bias currents follow a quadratic current–voltage (IV) relationship, and this is in agreement with space-charge-limited current transport theory. Our results confirm the effects of the growth conditions including oxygen overpressure and growth substrate on intrinsic carrier concentrations and, hence, electrical properties of ZnO thin films. We conclude that output characteristics of Si/ZnO junction devices can be adjusted by modifications of growth conditions to create p–n equivalent junctions. The results have significant contributions to the development of future ZnO-based devices.