Investigation of native defects in BaSi2 epitaxial films by electron paramagnetic resonance

Abstract

We investigated photoresponse, photoluminescence (PL), and electron paramagnetic resonance (EPR) spectra of 0.5 μm thick BaSi2 films grown by molecular beam epitaxy using various Ba-to-Si deposition rate ratios (R Ba/R Si). BaSi2 films (R Ba/R Si = 2.2) showed the highest photoresponsivity at room temperature. In contrast, BaSi2 films with R Ba/R Si away from 2.2 showed low photoresponsivity but intense sub-bandgap PL at 9 K. An anisotropic EPR line was observed below 20 K for such BaSi2 films. The EPR line disappeared for BaSi2 films passivated with atomic hydrogen. Thereby, the PL and EPR signals are interpreted to originate from native defects in the BaSi2 films.