Theoretical characterization of C doped SiGe monolayer

Abstract

Two dimensional Si1−xGeCx (SGC) alloys have been investigated within the framework of density functional theory using the hybrid functional of Heyd-Scuseria-Ernzerhof for the electron exchange correlation potential. The site occupancy disorder program is used to predict the most stable configuration for different values of carbon (C) concentration (x). With increasing C content, the lattice constant decreases almost linearly, while there is a reversal in the bandgap bowing for x>0.50. Besides the ideal solid solutions, we have also studied the effect of the C dimer. The calculated mixing enthalpy suggests that the growth of the alloys follows the endothermic reaction. The spinodal and binodal decomposition curves for Si and C rich phases have been explained along with a growth temperature equal to 2675 K. The valence and conduction band edges are aligned with respect to the vacuum level. The calculated optical absorption coefficient of SGC alloys is greater than 104cm−1, suggesting that these alloys are promising materials for opto-electronic applications. Our results may motivate experimentalists to synthesize these alloys which show promise for efficient thin film devices.