Achieving Background-Limited Performance with Light-Induced Band Inversion in a Room-Temperature BP/Ge Heterojunction

Abstract

Achieving Background-Limited Infrared Performance (BLIP) sets the ultimate standard for photodetector sensitivity, determined by unavoidable background radiation rather than intrinsic device noise. This threshold is critical for applications such as environmental monitoring and security systems. Traditional photodetectors, often limited by requirements for cryogenic cooling and precise lattice matching, do not suffice for practical scenarios. We introduce an approach using light-induced band inversion, exemplified by black phosphorus (BP) and germanium (Ge) heterojunction, which operates at room temperature. This method not only circumvents the need for complex environmental controls but also enhances performance under ambient conditions. The heterojunction's capability for dual photoresponse- producing both positive and negative outputs based on incident wavelength- is crucially bolstered by the suppression of carrier recombination at the interface. This advancement contributes to a low dark current density of approximately 1.2×10⁻⁶ A/cm² and a noise equivalent photon of 50, facilitating a peak detectivity of 9.81×10¹¹ cm⋅Hz^1/2⋅W⁻¹ at 3460 nm, reaching the BLIP limit within the band 3460 ~ 4000 nm. The broad applicability of light-induced band inversion indicates its potential as a universal strategy for enhancing photodetection across diverse platforms and wavelength domains, paving the way for unmatched sensitivity and reliability.