Al2O3 barrier layer for enhancing UV to visible rejection ratio in p-Si/n-MgZnO heterojunction visible blind UV photodetectors

Abstract

The fabrication of visible blind ultraviolet photodetectors based on p-Si/n-MgxZn1-xO heterojunction is challenging due to the generation of visible photoresponse caused by the drift of visible light generated electrons from p-silicon to n-MgxZn1-xO across the interface. Here, it is shown that by incorporating a thin ∼30 nm Al2O3 interlayer at the heterojunction, the UV-to-visible rejection ratio in p-Si/n-Mg0.25Zn0·75O photodetectors can be significantly enhanced. The Al2O3 interlayer inserted between n-Mg0.25Zn0·75O and p-Si serves as an effective blocking layer against the transport of visible light-generated electrons from p-Si to n-Mg0.25Zn0·75O, thereby suppressing the visible photoresponse. As a result, the UV-to-visible rejection ratio was improved by approximately three orders of magnitude, with a peak responsivity of 0.17 mA/W at 270 nm and a reverse bias of 0.5 V. This high degree of visible blindness of p-Si/n-Mg0.25Zn0·75O heterojunction photodetectors with an Al2O3 barrier layer holds promise for next-generation visible-blind UV photodetection applications.