EFFECT OF BISMUTH CONTENT ON THE STRUCTURAL AND ELECTRONIC PROPERTIES OF GaAs1-yBiy: FIRST PRINCIPLES CALCULATIONS

Abstract

A theoretical study of the effect of bismuth concentration on the structural and electronic properties of the GaAs1-yBiy solid solution is presented using the density functional theory in the VASP 5.4.4 software package. The results of the study showed that the fundamental band gap GaAs1-yBiy increase in the concentration of bismuth leads to an increase in the GaAs1-yBiy lattice constant, which causes internal asymmetry and a decrease in the Ga-Bi bond length. It has been shown that, with an increase in the number of Bi atoms substituting As atoms, a distortion of the position of neighboring Ga atoms and a decrease in the Ga-As bond length are observed at the sites of the crystal lattice. It has been established that these changes are due to the influence of the neighboring Bi atom, which affects the Ga-Bi bond length and reduces its length down to 2,6133 Å at y equal to 12,5%. The angle between the Ga-Bi and Ga-Bi bonds, on the contrary, increases with increasing Bi concentration and can reach a maximum value of 110,9256°. The combination of such structural changes in the crystal lattice of GaAs1-yBiy further lead to the emergence of potential defects in the form of clustering of Bi atoms or displacement of the Bi atom in the position of the interstitium. It has been established that supercells have the most stable configuration. GaAs1-yBiy with a concentration of Bi atoms up to 12,5%. The band gap of the GaAs1-yBiy solid solution decreases from 1,283 eV to 0,712 eV with increasing bismuth concentration from 1,85 mol.% to 12,5 mol.%. The band gap values obtained are, on the whole, close to known literature data. This shows that the direct band gap of this alloy covers the spectral region from the near infrared to the infrared range.