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 Si1-yPy decreases with higher P concentrations due to the incorporation of smaller P atoms, while that of Si1-yAsy and Si1-ySby 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 (X4V) is the most energetically favorable structure for Si:X for all n-type dopants. With most energetically favorable structure (P4V), the effect of the vacancy formation on the lattice parameter is greatly reduced, and thus the lattice parameters of P4 and P4V are similar. However, in case of As-and Sb-doped Si, we found that the relaxed lattice parameter in the form of Asn and Sbn 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 Xn. Both bond length and angle in X4V decrease compared to those of X4 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 P4V, As4V, and Sb4V 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.