Photoluminescence And Time-Resolved Photoluminescence Study Of Gase1-Xsx Mixed Crystal

GaSe1-xSx mixed crystals have recently drawn worldwide attention owing to their wide bandgap, which can be tuned by varying the ratio between Se and S. We have addressed the scarcity of comprehensive studies on its dynamic properties by investigating the photoluminescence (PL) and time-resolved photoluminescence (TRPL) of GaSe1-xSx (x = 0, 0.1, 0.2, 0.5) mixed crystals at different temperatures (14 - 300 K) using 404 nm excitation from a Ti:Sapphire laser. This paper aims to show that the PL spectra and the lifetime of GaSe1-xSx could be used to determine the stacking type and composition of the sample. Three Gaussian peaks were deconvoluted from the obtained PL spectrum and were attributed to excitons from the direct and indirect bandgaps. As the sulfur composition increases, the color of the emission changes and the PL spectra exhibits a blueshift. Selenium-rich samples, which have a epsilon-stacking, have an orange emission while sulfur-rich samples, which have a epsilon-beta mixed stacking, have a yellow to green emission. TRPL results reveal that the lifetime becomes longer as the sulfur composition increases. The stacking type influences the separation and transfer of the carriers. Hence, sulfur-rich samples have a significantly longer lifetime than selenium-rich samples due to their beta-stacking. As the temperature increases, the lifetime also becomes longer due to the increase of the non-radiative recombination rate, which plays a dominant role in the PL emission. These results are useful for the development of GaSe1-xSx-based optoelectronic devices in the red to the blue visible region.