Electronic Energy Structure of Sc-doped GaAs

Gallium arsenide (GaAs) exhibits a wide range of practical applications. Notably, it is extensively employed in optoelectronics, where it serves as a foundation for high-efficiency light-emitting diodes, laser diodes, photodetectors, and photovoltaic cells. Additional significant applications include radiation-resistant solar arrays, integrated circuits, and Hall-effect sensors, among others. In this study, we report the concentration dependence of the electronic energy structure for Sc-doped GaAs (Ga1 – xScxAs, x  1/32, 2/32 and 8/32). The calculations were performed within the Density Functional Theory (DFT) framework using the Generalized Gradient Approximation (GGA) with the Perdew–Burke–Ernzerhof (PBEsol) parametrization. The interaction between ions and valence electrons was described using norm-conserving pseudopotentials. Two alternative cases of Sc doping in GaAs (Ga1 – xScxAs, x  2/32) are investigated, which correspond to either cubic (the space group #215) or tetragonal (#115) structures. The energy band dispersion and the density of states are analyzed. It was found that the band gap is characterized by a direct transition at low (х ≤ 2/32) Sc concentrations, whereas it shifts to an indirect type at high (х  8/32) Sc doping levels. The energy band dispersion was analyzed based on the calculated effective masses of electrons (mc) and holes (mv). The effect of scandium doping on the electronic energy structure of GaAs was elucidated based on the partial density of states (PDOS) contributions. Issuing from the electronic energy spectrum, we calculate the real and imaginary components of the dielectric function. Finally, the fundamental optical properties of the Ga1 – xScxAs solid solutions are derived using the Kramers–Kronig relations, in particular the refractive index and the extinction and absorption coefficients.