Intrinsic Electric Field Driven High Sensitive Photodetection in Alloy TMDC MoSSe

TL;DR

This paper demonstrates that alloy TMDC MoSSe with an intrinsic electric field exhibits high sensitivity in photodetection due to enhanced electron-hole separation, broad spectral responsivity, and tunable response speed, advancing optoelectronic applications.

Contribution

It reveals the optoelectronic advantages of alloy TMDC MoSSe with an inherent dipole, including improved photodetection performance and tunable response modes, through experimental and theoretical analysis.

Findings

Extended exciton lifetime due to dipole-induced wavefunction separation

Broad spectral responsivity of the photodetector

Switchable response speed via photogating effect

Abstract

Alloying offers an effective way to improve the functionality of transition metal dichalcogenides (TMDCs) in both fundamental research and optoelectronic applications, as it allows for engineering their electronic and optical properties. This study investigates the optoelectronic properties of CVD-synthesized alloy MoSSe, which exhibits an inherent out-of-plane dipole moment, arising from asymmetry in S and Se atoms on either side of the Mo layer, as confirmed by piezoelectric force microscopy, polarization-resolved second harmonic generation studies and theoretical first-principles calculations. Time-resolved photoluminescence measurements reveal an extended exciton radiative recombination lifetime in MoSSe, attributed to electron-hole wavefunction separation by the dipole moment, which improves photodetection by facilitating enhanced electron-hole separation before recombination. The device demonstrates significant responsivity over broad spectral range. By employing the photogating effect, the device response can be switched from slow to fast modes. These findings are further supported by illumination intensity-dependent photoluminescence and Raman measurements, underscoring the potential of polar TMDCs in future optoelectronic devices.