Study of a neutron-resistant p+-Si/n-ZnO photodetector with avalanching gain

Abstract

The photo detection properties under large reverse bias voltage and neutron irradiation effects of the p+-Si/n-ZnO photodetector were investigated. Intrinsic defects, VO, VZn, and Oi, were observed in the non-irradiated ZnO film from the photoluminescence spectroscopy. The neutron induced defects in the neutron irradiated ZnO film reacted with the VZn, Oi and grain boundary defects resulting in the degradation of mid band emissions. The p+-Si/n-ZnO heterojunction shows a rectifying factor of >1000 at 300 K under ±1.5 V and an avalanche breakdown voltage of ∼13 V. The impact ionization process is taken place in the p+-Si region revealed from the numerical calculation of the breakdown voltage of the p+-Si/n-ZnO heterojunction. The device can well perform as a linear and fast response photodetector with good repeatability. When operating under large reverse bias voltage, the p+-Si/n-ZnO can also act as an avalanching photodiode with the avalanche gain of ∼ 30. The p+-Si/n-ZnO detector continues to be operative as an avalanche photodiode as well after neutron irradiation with the fluence of 1015 n/cm2 unless the gain degenerating to ∼10, indicating the good neutron tolerance of the p+-Si/n-ZnO photodetector.