Investigation of defect levels in BaSi2 epitaxial films by photoluminescence and the effect of atomic hydrogen passivation

Photoluminescence (PL)measurements were carried out on 0.5-μmthick BaSi2 epitaxial films grown on Si(111) substrates with various Ba-to-Si deposition rate ratios (RBa/RSi) in the range of 1.7–5.1. The samples were excited fromboth the frontside (BaSi2) and the backside (Si substrate), at temperatures in the range of 8–50 K. Thesemeasurements have highlighted the existence of localized states within the bandgap that result fromdefects in the BaSi2 films. The PL intensity is highly dependent on the excitation power, temperature, andRBa/RSi. Of those studied, the BaSi2 film atRBa/RSi=4.0 showed themost intense PL andweak photoresponsivity, whereas the PL intensity wasweaker for the other samples. Therefore, we chose this sample for a detailed PL investigation. Based on the results we determined the energy separation between localized states, corresponding to PL peak energies. The difference in PL spectra excited from the BaSi2-side and Si-side is attributed to the difference in kinds of defects emitting PL. The photoresponsivity of the BaSi2 was drastically enhanced by atomic hydrogen passivation, and the PL intensity of the sample decreased accordingly.