Piezoresistance in silicon at uniaxial compressive stresses up to 3 GPa

TL;DR

This study investigates the piezoresistance of silicon under high uniaxial compressive stress up to 3 GPa, revealing different saturation behaviors in n-type and p-type silicon with implications for strained silicon technologies.

Contribution

It provides the first detailed experimental and theoretical analysis of silicon's piezoresistance behavior up to 3 GPa, especially highlighting the non-saturation in p-type silicon.

Findings

n-type silicon conductance saturates at about 45% of zero-stress value

p-type silicon conductance increases beyond predicted limits without saturation

ab-initio calculations show no saturation of conductance or mobility below 3 GPa

Abstract

The room-temperature longitudinal piezoresistance of n-type and p-type crystalline silicon along selected crystal axes is investigated under uniaxial compressive stresses up to 3 GPa. While the conductance ($G$) of n-type silicon eventually saturates at $\approx 45%$ of its zero-stress value ($G_0$) in accordance with the charge transfer model, in p-type material $G/G_0$ increases above a predicted limit of $\approx 4.5$ without any significant saturation, even at 3 GPa. Calculation of $G/G_0$ using \textit{ab-initio} density functional theory reveals that neither $G$ nor the mobility, when properly averaged over the hole distribution, saturate at stresses lower than 3 GPa. The lack of saturation has important consequences for strained silicon technologies.