Single crystal growth and characterization of copper aluminum indium disulfide chalcopyrites

Single crystals of Cu(AlxIn1−x)S2 (0≤x≤1) with x=0, 0.2, 0.4, 0.5, 0.6, 0.7, and 1.0 were grown by chemical vapor transport method using ICl3 as a transport agent. The results of X-ray measurement indicated that the as-grown crystals are single phase and isostructural. The formation of {1 1 2} face is preferable for the crystallization of whole series Cu(AlxIn1−x)S2 (0≤x≤1) chalcopyrite crystals. Electronic structure of Cu(AlxIn1−x)S2 (0≤x≤1) was probed experimentally by X-ray photoelectron spectroscopy (XPS) and thermoreflectance (TR) measurements. The experimental results enabled to identify the electron configuration, and determine energies of valence and conduction band edges of the chalcopyrites. The energies of near-band-edge transitions in the Cu(AlxIn1−x)S2 (0≤x≤1) were determined accurately by TR measurements. Composition dependences of transition energies near band edge were evaluated. The obtained energies were assigned to the particular interband transitions of Cu(AlxIn1−x)S2 (0≤x≤1). Based on the experimental analyses of TR and XPS, the electronic band structure near the fundamental band edge of Cu(AlxIn1−x)S2 (0≤x≤1) was thus constructed. The good correspondence of the TR and XPS results as well as the proposed band diagram verifies the crystalline quality of the chalcopyrites.