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

The photo detection properties under large reverse bias voltage and neutron irradiation effects of the p⁺-Si/n-ZnO photodetector were investigated. Intrinsic defects, V_O, V_Zn, and O_i, 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 V_Zn, O_i 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.