Temperature dependent electrical transport in p-ZnO/n-Si heterojunction formed by pulsed laser deposition

ZnO film, with urea as nitrogen source to dope its p-type, is deposited by pulsed laser on n-type (100) Si substrate to fabricate p-ZnO/n-Si heterojunctions. The current-voltage (I-V) characteristics of the heterojunction have been studied in the temperature range 140-300 K. The turn on voltage decreased with increasing temperature while the breakdown voltage is increased slightly. The forward current is greatly increased with increasing temperature, while the reverse current is increased nominally. Both the decrease in barrier height and the increase in ideality factor with decrease in temperature are indicative of deviation from the pure thermionic emission-diffusion mechanism. The ln(I-0) versus 1/kT plot exhibits the linear portion corresponding to an activation energy of 0.07 eV. Temperature-dependent forward current measurements suggest that trap-assisted multistep tunneling is the dominant carrier transport mechanism in this heterojunction. C-V analysis indicates an abrupt interface and band bending of 0.96 V in silicon. Heterojunction band diagram for p-ZnO/n-Si is proposed. The hysteresis in the high frequency capacitance voltage (C-V) curve indicates the presence of trapped charges at the interface.