Comparison of Process of Diffusion of Interstitial Oxygen Atoms and Interstitial Hydrogen Molecules in Silicon and Germanium Crystals: Quantumchemical Simulation

TL;DR

This study uses quantumchemical simulations to analyze and accurately predict the diffusion behaviors of interstitial oxygen atoms and hydrogen molecules in silicon and germanium crystals, aligning well with experimental data.

Contribution

It provides the first detailed quantumchemical description of diffusion constants and activation energies for oxygen and hydrogen in Si and Ge, including pressure effects.

Findings

Calculated activation energies and diffusion constants match experimental data.

Diffusion of oxygen is cooperative and lattice-dependent.

Hydrogen diffusion involves molecular rotation and fluctuation effects.

Abstract

The theoretical analysis of the process of diffusion of interstitial oxygen atoms and hydrogen molecules in silicon and germanium crystals has been performed. The calculated values of the activation energy and pre-exponential factor for an interstitial oxygen atom Ea(Si) = 2.59 eV, Ea(Ge) = 2.05 eV, D(Si)= 0.28 cm2s-1, D(Ge)= 0.39 cm2s-1 and interstitial hydrogen molecule Ea(Si) = 0.79-0.83 eV, Ea(Ge) = 0.58-0.62 eV, D(Si)= 7.4 10(-4) cm2s-1, D(Ge)= 6.5 10(-4) cm2s-1 are in an excellent agreement with experimental ones and for the first time describe perfectly an experimental temperature dependence of an interstitial oxygen atom and hydrogen molecules diffusion constant in Si and Ge crystals. It is shown, that for a case of impurity atom with a strong interaction with a lattice (interstitial oxygen atom) process of diffusion has a cooperative nature - the activation energy and pre-exponential are controlled by the optimum position of three nearest lattice atoms. For a case of extended defect with a weak interaction (an interstitial hydrogen molecule) process of diffusion is determined by the activation barrier subjected to fluctuations connected with rotation of a hydrogen molecule. The effect of hydrostatic pressure on the process of diffusion is discussed also.