High-performance near-infrared PtSe2/n-Ge heterojunction photodetector with ultrathin Al2O3 passivation interlayer

Two-dimensional (2D) materials are being intensively exploited for broadband-responsive photodetectors (PDs). However, the broadband-responsive PDs based on 2D materials normally suffer from poor response to infrared wavelengths. Here, we report the excellent photoresponse performance of vertical PtSe2/ultrathin Al2O3/Ge PD under near-infrared illumination. We directly selenize Pt film deposited on Al2O3/Ge to form PtSe2 layer. The ultrathin Al2O3 passivation layer plays the role of surface modification, effectively weakening recombination of the photogenerated carriers. Under 1550-nm illumination, the PtSe2/ultrathin Al2O3/Ge PD with a working area of 50 mu m x 50 mu m at zero bias obtains a large responsivity of 4.09 A W-1, and fast rise/ fall times of 32.6/18.9 mu s, respectively. And under an external electric field of -5 V, the responsivity and response speed of the PtSe2/ultrathin Al2O3/Ge PD can be as high as 38.18 A W-1 and as fast as 9.6/7.7 mu s, respectively. We find that the working area has a great influence on the photoresponse characteristics. Furthermore, we demonstrate the PtSe2/ultrathin Al2O3/Ge PDs array shows outstanding violet, visible, and infrared imaging capability at room temperature. Our study suggests that the PtSe2/ultrathin Al2O3/Ge heterojunction has great application prospects for the design of emerging broadband optoelectronic devices with superior performance for near-infrared response.

Automated summary

We report the excellent photoresponse performance of a vertical PtSe2/ultrathin Al2O3/Ge photodetector under near-infrared illumination. The PtSe2 layer is formed by directly selenizing a Pt film deposited on Al2O3/Ge. The ultrathin Al2O3 passivation layer effectively weakens carrier recombination and enhances the device's responsivity and response speed.