The effect of strain on tunnel barrier height in silicon quantum devices

Abstract

Semiconductor quantum dot (QD) devices experience a modulation of the band structure at the edge of lithographically defined gates due to mechanical strain. This modulation can play a prominent role in the device behavior at low temperatures, where QD devices operate. Here, we develop an electrical measurement of strain based on I (V) characteristics of tunnel junctions defined by aluminum and titanium gates. We measure relative differences in the tunnel barrier height due to strain consistent with experimentally measured coefficients of thermal expansion (α) that differ from the bulk values. Our results show that the bulk parameters commonly used for simulating strain in QD devices incorrectly capture the impact of strain. The method presented here provides a path forward toward exploring different gate materials and fabrication processes in silicon QDs in order to optimize strain.