Sensitive infrared surface photovoltage in quasi-equilibrium in a layered semiconductor at low-intensity low-temperature condition

TL;DR

This study demonstrates a highly sensitive infrared surface photovoltage in NbSi0.5Te2 at low temperature and low light intensity, revealing new potential for layered semiconductors in infrared optoelectronics.

Contribution

It reports the first observation of ultra-sensitive infrared SPV in NbSi0.5Te2 under quasi-equilibrium conditions at low temperature and intensity.

Findings

Photoresponsivity up to 2.4×10^6 V/(W·cm^(-2)) at LILT

Confirmation of Dember effect in the system

Intrinsic carrier freezing enhances photoresponse

Abstract

Benefit to layer-dependent bandgap, van der Waals materials with surface photovoltaic effect (SPV) enable photodetection over a tunable wavelength range with low power consumption. However, sensitive SPV in the infrared region, especially in a quasi-steady illumination condition, is still elusive in layered semiconductors. Here, using angle-resolved photoemission spectroscopy, we report a sensitive SPV in quasi-equilibrium in NbSi0.5Te2, with photoresponsivity up to 2.4*10^6 V/(W*cm^(-2)) at low intensity low temperature condition (LILT). The sensitive SPV is further confirmed by observing the Dember effect, where the photogenerated carrier density is high enough and diffusion currents suppress SPV. Temperature-dependent measurements indicate that intrinsic carriers freezing at low temperature leads to the ultrahigh photoresponse, while a small amount of photon-generated carriers in quasi-equilibrium dominate the system. Our work not only provides a promising layered semiconductor for Infrared optoelectronic devices with strong infrared SPV at LILT, which has application potential in fields such as quantum information and deep-space exploration, but also paves a novel way to enhance light-matter interaction effect by freezing bulk carriers.