The steady-state, space-charge-limited piezoresistance (PZR) of defect-engineered, silicon-on-insulator device layers containing silicon divacancy defects changes sign as a function of applied bias. Above a punch-through voltage ($V_t$) corresponding to the onset of a space-charge-limited hole current, the longitudinal $⟨110⟩$ PZR $\pi$ coefficient is $\pi \approx 65\times {10}^{-11}$ $\mathrm{Pa}$${}^{-1}$, similar to the value obtained in charge-neutral, $p$-type silicon. Below $V_t$, the mechanical stress dependence of the Shockley-Read-Hall (SRH) recombination parameters, specifically the divacancy trap energy $E_T$ that is estimated to vary by approximately $30\mu \mathrm{V}/$MPa, yields $\pi \approx -25\times {10}^{-11}$ $\mathrm{Pa}$${}^{-1}$. The combination of space-charge-limited transport and defect engineering that significantly reduces SRH recombination lifetimes makes this work directly relevant to discussions of giant or anomalous PZR at small strains in nanosilicon whose characteristic dimension is larger than a few nanometers. In this limit the reduced electrostatic dimensionality lowers $V_t$ and amplifies space-charge-limited currents and efficient SRH recombination occurs via surface defects. The results reinforce the growing evidence that in steady state, electromechanically active defects can result in anomalous, but not giant, PZR.

• Received 22 October 2020
• Revised 1 January 2021
• Accepted 5 January 2021

DOI:https://doi.org/10.1103/PhysRevApplied.15.014046