Blocking Si-Induced Visible Photoresponse in n-MgxZn1-xO/p-Si Heterojunction UV Photodetectors Using MgO Barrier Layer

Photodetectors based on n-Mg0.25Zn0.75O/p-Si heterojunctions are not only suitable for integration with existing semiconductor technology, but also circumvent the difficulty of stable p-type doping in MgxZn1-xO. However, the use of Si leads to photoresponse in the visible part of the light spectrum, which renders n-MgxZn1-xO/p-Si heterojunction devices unsuitable for visible blind UV photodetection. Herein, it is demonstrated that the visible photoresponse in the n-Mg0.25Zn0.75O/p-Si photodetectors can be significantly suppressed by inserting a thin interlayer of MgO at the heterojunction. The MgO layer serves as a blocking layer for the drift of photo-excited electrons from p-Si to n-Mg0.25Zn0.75O, thereby limiting the visible photoresponse. It is found that on increasing the thickness of the MgO interlayer from 3 to 15 nm, the UV to visible rejection ratio increases from approximate to 25 to 200. This enhancement in the UV to visible rejection ratio demonstrates that n-Mg0.25Zn0.75O/p-Si heterojunction devices with MgO interlayer are promising for visible-blind UV photodetection applications.