Anisotropy of the spectroscopy properties of the wurtz-stannite Cu sub(2ZnGeS) sub(4) single crystals

In this study, the near band edge anisotropic optical properties of wurtz-stannite (WS) Cu sub(2ZnGeS) sub(4) single crystals were characterized using polarization-dependent transmittance and electrolyte electroreflectance (EER) techniques. Single crystals of Cu sub(2ZnGeS) sub(4) were grown by chemical vapor transport method using iodine as a transport agent. Analysis of absorption spectra revealed indirect allowed transitions for Cu sub(2ZnGeS) sub(4) with the band gaps of 2.02 (2.07) and 2.08 (2.14) eV for Ea-b and Da-a polarization configurations at 300 (10) K. The room-temperature EER spectra in the vicinity of the direct band edge showed anisotropic transitions at around 2.38, 2.44 and 2.45 eV for Ea-b, Da-a and Da-c polarizations, respectively. Based on the experimental observations and recent band-structure calculations a plausible band diagram near band edge of WS-Cu sub(2ZnGeS) sub(4) was constructed.