Photoresponse measurement of highly oriented BaSi2 films on Ge(111) using solid phase epitaxy templates

We fabricated 850-nm-thick BaSi
₂
films on p-Ge(111) substrates by molecular beam epitaxy using the template grown by solid phase epitaxy (SPE), and characterized their crystalline qualities and photoresponse properties. We succeeded to grow almost a-axis-oriented BaSi
₂
films on the SPE-BaSi
₂
templates. The root-mean-square of the surface roughness was approximately 5.8 nm. This value was much smaller than the grown layer thickness. Hence, it is safe to state that the grown BaSi
₂
is a continuous film. Photoresponse spectra were clearly observed for photons with energies greater than the band gap of BaSi
₂
(ca. 1.3 eV at room temperature). We achieved an external quantum efficiency up to 15% at 1.55 eV under a forward bias voltage of 2.0 V applied across the top and bottom electrodes.