Optical spectra and energy band structure of layer‐type A^IVB^VI compounds

Abstract

Abstract The electroreflectance and absorption spectra as well as the hydrostatic pressure dependence of the fundamental absorption edge of GeS, GeSe, SnS, and SnSe crystals are investigated in polarized light. The lowest direct energy gaps are found to be 1 V 1— 1 V 1 (E | | a) and 1 Λ 4— 1 Λ 4 (E || b) for Ge and Sn monochalcogenides, respectively. The pressure coefficient of the energy gap 1 Λ 4— 1 Λ 4 dE/AP = = — (1.3 ± 0.1) × 10 −4 eV/MPa of SnSe and SnS is almost twice larger than that of the gap 1 V 1— 1 V 1 in GeSe, GeS, and SnSe. On the basis of these investigations, different absorption mechanisms responsible for the fundamental absorption edge are discussed.