Carrier Recirculation Induced Ultrasensitive Photodetectors of InSe/CdTe Heterostructure Featuring an Interfacial Holes Layer

Photodetectors (PDs) based on mix-dimensional heterojunctions (MDHJs) built from 2D layered materials and covalent-bonded semiconductors show the prospect of compensating the intrinsic weakness of 2D materials to realize their full potential. However, there is an open issue to improve the temporal response of PDs while maintaining high gain and sensitivity. Herein, photoconductive type MDHJs PDs with 2D InSe and covalent-bonded CdTe thin film are designed and fabricated in which InSe is the active layer and CdTe is the medium gain one. The conductivity of InSe is improved by exceeding 50 times led by the formation of p-p heterojunction because of that an interfacial hole accumulation at InSe side and a built-in field at CdTe one are formed. Benefiting from the synergistic function of photoconductive and photogating effects, carrier recirculation induced responsitivity, detectivity, and external quantum efficiency with orders of magnitude increment reach 4.31 × 10⁴ AW^-1, 7.55 × 10¹³ Jones and 1.01 × 10⁷%, and more optimal response time than those of other InSe PDs is demonstrated. This device construction strategy with exceptional performance hints at the prospect of optoelectronic devices of 2D InSe.