Cálculo da massa efetiva dos portadores de carga dos sólidos cristalinos

Abstract

In this work, calculations were performed to determine the effective mass of the charge carriers of the GaAs and InP semiconductors. The calculations were performed using electronic structure methods based on the Density Functional Theory implemented in the Elk computational code. For the exchange and correlation energy, the generalized gradient approximations (GGA) and the modified Becke-Johnson exchange potential (mBJ) were used. The objectives of this work are: (1) to understand how the effective mass of charge carriers can be calculated using the aforementioned calculation methodologies and (2) to verify whether the implementation of these methods to determine the effective mass in the Elk computational code is satisfactory. The choice of GaAs and InP compounds is due to the fact that the effective mass of their charge carriers is well documented in the literature, both from a theoretical-computational and experimental point of view. Initially, the band structures of the materials were determined from which we inferred that they have a direct band gap at the gamma point as predicted experimentally. From this evaluation, the effective masses of the carriers were determined. The calculations performed showed that the effective mass of the charge carriers can be determined in the same order of magnitude as the experimental result using both GGA and mBJ approximations. It was found that the GGA results are underestimated and the mBJ are overestimated in relation to the experimental one. This behavior was also verified in a previous work that carried out calculations of the GaAs and InP charge carriers using another computer code with an electronic structure method different from the one used in this work. Finally, it is verified that the methodology and the computational tool adopted in this work are reliable for the determination of the effective masses of the charge carriers of the crystalline solids.