A proof of concept of the bulk photovoltaic effect in non-uniformly strained silicon

We numerically investigate non-uniformly strained Si-based systems to demonstrate that when a well focused laser beam locally excites the sample, the lattice distortion, impacting the band edge profile, causes a spatially dependent photovoltaic effect. It follows that, scanning the sample surface with the pump spot, a photovoltage signal can be acquired and used to quantitatively map the non-uniform strain field. To provide numerical evidence in this direction, we combine mechanical simulations with deformation potential theory to estimate the band edge energy landscape of a Si lattice strained by an array of SiN stripes fabricated on the top surface. These data are then used to simulate the voltage signal obtained scanning the sample surface with a normal incident pump beam. Our analysis suggests that strain deformations as small as 0.1% can trigger at room temperature robust photovoltaic signals. These results allow us to envision the development of a fast, cost-effective, and non-destructive setup, which leverages on the bulk-photovoltaic effect to image the lattice deformation in semiconductor crystals.