Electric Field Control of Shallow Donor Impurities in Silicon

TL;DR

This study uses tight-binding simulations to analyze how electric fields influence shallow donor impurities in silicon, revealing ionization regimes and implications for quantum computing architectures.

Contribution

It demonstrates the effectiveness of tight-binding models for donor impurities in silicon and explores electric field-induced ionization regimes relevant for quantum device design.

Findings

Adiabatic ionization possible for impurities ~5 nm below barrier within 1 ps

No adiabatic ionization for impurities ~10 nm or more below barrier

Results inform design of silicon-based quantum computers

Abstract

We present a tight-binding study of donor impurities in Si, demonstrating the adequacy of this approach for this problem by comparison with effective mass theory and experimental results. We consider the response of the system to an applied electric field: donors near a barrier material and in the presence of an uniform electric field may undergo two different ionization regimes according to the distance of the impurity to the Si/barrier interface. We show that for impurities ~ 5 nm below the barrier, adiabatic ionization is possible within switching times of the order of one picosecond, while for impurities ~ 10 nm or more below the barrier, no adiabatic ionization may be carried out by an external uniform electric field. Our results are discussed in connection with proposed Si:P quantum computer architectures.