Band alignments at native oxide/BaSi2 and amorphous-Si/BaSi2 interfaces measured by hard x-ray photoelectron spectroscopy

We fabricated native oxide/BaSi
₂
and amorphous Si(a-Si, 5 nm) structures on n-Si(111) by molecular beam epitaxy and evaluated the band alignments at the interfaces by x-ray photoelectron spectroscopy in order to understand the carrier transport properties. We found that the potential barrier height of the native oxide for the minority-carriers, holes, in n-BaSi
₂
is approximately 3.9 eV, whereas that of a-Si is approximately -0.2 eV. These results mean that a-Si layer is superior to the native oxide from the viewpoint of hole transport. Thanks to these band alignment, the photoresponsivity was drastically improved for the BaSi
₂
capped with the a-Si layer.