Quantum Electronic Strengthening of Covalent Semiconductor Materials by Excess Electron/Hole Doping

Abstract

Covalent semiconductor materials are indispensable for the development of modern society because of their excellent semiconductor properties, but they are consistently challenged by failures due to brittle fracture. Recently, both experimental and theoretical attempts to modify the strength of materials by electron doping have been reported. Here, we comprehensively examine the impact of excess electrons and holes on the bonding strength of a typical covalent material based on first-principles calculations. The bond strength is reduced or increased monotonically and linearly with electron doping density, resulting in an approximate 60% variation at the highest feasible doping density. The degree of strength change per carrier density for each material is found to correlate with its bonding characteristics, with stronger ionic bonding properties exhibiting larger changes. Furthermore, the quantum mechanism of the change in strength is explained by energetic contribution of bonding orbitals occupied by introduced charge. These results indicate that covalent semiconductor materials share a common mechanism of strengthening by electron doping, which could contribute to the design of more robust semiconductor products.