Investigation of defect levels in BaSi 2 epitaxial films by photoluminescence and the effect of atomic hydrogen passivation

Photoluminescence (PL) measurements were carried out on 0.5- μ m thick BaSi 2 epitaxial films grown on Si(111) substrates with various Ba-to-Si deposition rate ratios ( R Ba / R Si ) in the range of 1.7–5.1. The samples were excited from both the frontside (BaSi 2 ) and the backside (Si substrate), at temperatures in the range of 8–50 K. These measurements have highlighted the existence of localized states within the bandgap that result from defects in the BaSi 2 films. The PL intensity is highly dependent on the excitation power, temperature, and R Ba / R Si . Of those studied, the BaSi 2 film at R Ba / R Si = 4.0 showed the most intense PL and weak photoresponsivity, whereas the PL intensity was weaker 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 BaSi 2 -side and Si-side is attributed to the difference in kinds of defects emitting PL. The photoresponsivity of the BaSi 2 was drastically enhanced by atomic hydrogen passivation, and the PL intensity of the sample decreased accordingly.