Photoluminescence of two-dimensional GaTe and GaSe films

Abstract

Gallium chalcogenides are promising building blocks for novel van der Waals heterostructures. We reportonthe low-temperature micro-photoluminescence (PL) of GaTe and GaSefilms with thicknesses ranging from 200 nm toasingle unit cell.Inboth materials,PL shows adramatic decrease by 104-105 when film thicknessis reduced from 200to10 nm. Basedon evidence from continuouswave (cw) and time-resolved PL, wepropose amodel explaining the PLdecrease as a result of nonradiative carrier escape via surface states. Our results emphasize the need for special passivation of two-dimensional films for optoelectronic applications.