Room-temperature photoluminescence in quasi-2D TlGaSe2 and TlInS2 semiconductors

Abstract

We reveal the intrinsic band-to-band photoluminescence (PL) in Tl-based anisotropic semiconductors by means of confocal spectroscopy. The PL achieves largest value for k ⊥ c, where c is the layers stacking axis, and is dependent on polarization. In TlGaSe2, the band edge absorption spectra were determined at different excitation geometry by using techniques of depth-resolved free-carrier absorption (FCA) and photoacoustic response (PAR). A strong absorption enhancement is detected in a large spectral area in the near-surface region lateral to ab plane. The band-to-band absorption enhancement is the most probable cause for high PL intensity. The near-surface behavior, different from the bulk, might implement useful photonic functionality at room temperature (RT).