Electrical conductivity tuning and valence band splitting studies in Copper Gallium Selenide thin films

Copper gallium selenide (CGS) semiconductor thin films are suitable for various optoelectronic devices due to their stoichiometry dependent properties. Tuning of electrical conductivity (0.5–90 S/cm) by compositional variations of CGS thin films prepared by reactive evaporation of the three elements under vacuum is presented here. This p-type absorber material withstands its conductivity type over the entire range of compositional variation. The structure, morphology, elemental composition, chemical states, electrical and optical properties of the thin films are characterized using techniques like X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, UV–visible absorption spectroscopy and Hall effect measurements. Optical studies of the films reveal a three-fold absorption from which crystal field splitting ∼0.06 eV and spin orbit splitting ∼0.09–0.17 eV are determined. The optical fundamental absorption edges of the films vary from 1.6 to 1.67 eV. - Highlights: • CGS films well characterized by XRD, Raman, XPS, EDAX and SEM. • Grouping done based on anion/cation ratio for conductivity changes with composition. • Crystal field and spin orbit splitting parameters from optical absorption data.