Optical absorption in GaTe under high pressure

This paper reports on the pressure dependence at room temperature of the absorption coefficient of the layered semiconductor gallium telluride. The absorption edge in the explored pressure range (up to 6.1 GPa) can be accounted for through the superposition and interaction of a direct gap and an indirect gap. The pressure shift of the direct gap is strongly nonlinear, starting at low pressure with a coefficient of -85.7±0.4meV/GPa and exhibiting a minimum at around 2.9 GPa. The exciton binding energy decreases under pressure, which can be related to the increase of the dielectric constant. The broadening of the exciton line is explained through phonon-assisted intervalley scattering of conduction-band electrons after the crossover between direct and indirect gaps, with an estimation of the related intervalley deformation potential.