Impact of Cu substitution on structural, electronic, and optical properties of CdCuTe single crystals

We have experimentally investigated the effects of Cu substitution (0≤x≤0.03) on structural, electronic, and optical properties of bulk Cd1−xCuxTe, grown by Bridgman method, which is an important semiconductor for photovoltaic applications. A series of X-ray experiments unambiguously demonstrates high-quality Cd1−xCuxTe single crystals oriented along a (110) direction without clusters and/or secondary phases. Ultraviolet photoelectron spectroscopy reveals that the work function of Cd1−xCuxTe is only slightly smaller than that of CdTe. Although the Cu incorporation does not significantly alter the crystal structure, we find that the measured bandgap varies in the range from 1.474 to 1.461 eV at room temperature, which is suitable for photovoltaic applications. Together with the one-photon absorption coefficient, crucial optical parameters describing the temperature dependence of the bandgap are determined based on three analytical models.