Frist-Principle Study Of The Electronic Band Structure And The Effective Mass Of Ga_xIn_1-xP Ternary Alloy

With the advancement of science and technology, the group III-V semiconductors and their alloys are of practical interest and the range of technical applications of such semiconductors is extremely wide. As a kind of ternary alloys, GaxIn1-xP has the advantages of a low band gap, high electron mobility, strong anti-radiation and high energy conversion efficiency. GaxIn1-xP has been widely applied in optoelectronic and electronic devices, for example in the field of optoelectronic device fabrication, fiber optic communications, satellite, thermal photovoltaic power and so on. With the rise and rapid development of computational materials science, and its optical characteristics are essentially decided by the electronic structure. Therefore, the theoretical study of electronic structure and optical properties of the ternary alloys system have become an important means of mining GaxIn1-xP application, which have great significant implications for the development of new optoelectronic materials. In addition, the effect of the alloy composition on physical properties is important and should been investigated in detail to improve the performance of ternary alloys GaxIn1-xP and broaden its application fields.In this work, the electronic band structure and the effective mass of GaxIn1-xP ternary alloy are studied by the first principle calculation within the framework of the density functional theory. The software QUANTUM ESPRESSO and the generalized gradient approximation (GGA) for the exchange correlations have been used in the calculations. We present the calculated results of the equilibrium lattice parameter, band gap and effective mass of GaxIn1-xP for the Ga composition x varying from 0.0 to 1.0 by the step of 0.125. The effect of the Ga composition on the lattice parameter and the electronic density of states are discussed. The results show that the lattice parameter varies with the composition almost linearly following the Vegard’s law. A direct-to-indirect band-gap crossover is found to occur close to x= 0.7. The effective masses are also calculated along F (000) symmetry point. The results show that the band gap and the electron effective mass vary nonlinearly with composition x. The values of band gap obtained by calculating are smaller than the values of experiment. This is a prevalence of the problem when we use the density functional theory to calculate ternary alloys. Therefore, we have corrected the band gap based on the method of scissors operator and the values of correction are in line with the experiment, which verifies the correctness of the calculation method. Finally, the optical properties of the ternary mixed crystal system of GaxIn1-xP are studied, including the complex dielectric function and absorption coefficients. From the results, we can find that the static dielectric constant of the GaxIn1-xP system increases with increasing Ga composition x. There is a clear blue shift at the absorption band edge. Combined with the electronic structure, we can make a qualitative explanation for the changing of optical properties of GaxIn1-xP system, which is induced by the element of Ga.