Effect of N-type doping and vacancy formation on the thermodynamic, electrical, structural, and bonding properties of Si: X. (X = P, As, and Sb): a theoretical study

We investigated the effect of n-type doping and vacancy formation on the thermodynamic, electrical, structural, and bonding properties of Si:X (X = P, As, and Sb) using first-principles calculations. Density functional theory calculations show that the lattice parameter of Si 1 − y P y decreases with higher P concentrations due to the incorporation of smaller P atoms, while that of Si 1 − y As y and Si 1 − y Sb y increases with higher As and Sb concentrations. Moreover, both local density functional approximation and GGAgeneralized gradient approximation –Perdew, Burke, and Ernzerhof functionals demonstrate that donor-vacancy complex (X 4 V) is the most energetically favorable structure for Si:X for all n-type dopants. With most energetically favorable structure (P 4 V), the effect of the vacancy formation on the lattice parameter is greatly reduced, and thus the lattice parameters of P 4 and P 4 V are similar. However, in case of As- and Sb-doped Si, we found that the relaxed lattice parameter in the form of As n and Sb n is not strongly influenced by the environment around V. For all n-type dopants, the relaxed lattice parameter is same, regardless of the dopant distribution such as random alloys or X n . Both bond length and angle in X 4 V decrease compared to those of X 4 due to the greater electron repulsions caused by one lone pair of two electrons in the nonbonding region. Direct observation of the lone electron pair in P 4 V, As 4 V, and Sb 4 V using ELF shows that the vacancy plays a critical role in determining the structural and electrical properties of Si materials doped with n-type dopants. Theoretical findings in this study help to understand and predict the materials properties of Si doped with n-type atoms in fundamental researches as well as in industrial applications.