Thickness-modulated in-plane Bi₂O₂Se homojunctions for ultrafast high-performance photodetectors*

Abstract

Bi 2 O 2 Se thin film could be one of the promising material candidates for the next-generation electronic and optoelectronic applications. However, the performance of Bi 2 O 2 Se thin film-based device is not fully explored in the photodetecting area. Considering the fact that the electrical properties such as carrier mobility, work function, and energy band structure of Bi 2 O 2 Se are thickness-dependent, the in-plane Bi 2 O 2 Se homojunctions consisting of layers with different thicknesses are successfully synthesized by the chemical vapor deposition (CVD) method across the terraces on the mica substrates, where terraces are created in the mica surface layer peeling off process. In this way, effective internal electrical fields are built up along the Bi 2 O 2 Se homojunctions, exhibiting diode-like rectification behavior with an on/off ratio of 10 2 , what is more, thus obtained photodetectors possess highly sensitive and ultrafast features, with a maximum photoresponsivity of 2.5 A/W and a lifetime of 4.8 μs. Comparing with the Bi 2 O 2 Se uniform thin films, the photo-electric conversion efficiency is greatly improved for the in-plane homojunctions.