Optical properties of two-dimensional gallium chalcogenide films

TL;DR

This study investigates the optical properties of ultra-thin gallium chalcogenide films, revealing a significant decrease in photoluminescence with reduced thickness, attributed to surface-related non-radiative carrier escape.

Contribution

It provides the first detailed low-temperature PL analysis of GaTe and GaSe films down to a single unit cell, introducing a model for PL quenching in ultra-thin layers.

Findings

PL decreases by 10^4-10^5 when thickness reduces from 200 nm to 10 nm

Surface states facilitate non-radiative carrier escape in thin films

Model explains the dramatic PL quenching in ultra-thin gallium chalcogenide films

Abstract

Gallium chalcogenides are promising building blocks for novel van der Waals heterostructures. We report low-temperature micro-photoluminescence (PL) of GaTe and GaSe films with thickness ranging from from 200 nm to a single unit cell. In both materials, PL shows dramatic decrease by 10$^4$-10$^5$ when film thickness is reduced from 200 to 10 nm. Based on evidence from cw and time-resolved PL, we propose a model explaining the PL decrease as a result of non-radiative carrier escape via surface states.