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We demonstrated the marked photoresponsivity enhancement of BaSi2 epitaxial films by 5 min post-annealing at 850 °C–1000 °C in contrast to those at 600 °C–800 °C. Post-annealing at 1000 °C increased the photoresponsivity up to 9.0 A W−1 at a wavelength of around 800 nm under a bias voltage of 0.5 V applied between the top and bottom electrodes. The hole concentration decreased monotonously with annealing temperature from 8.3 × 1016 to 5.4 × 1015 cm–3, and the mobility exceeded 1000 cm2 V–1 s–1. The a-axis orientation of the BaSi2 films was significantly deteriorated at temperatures higher than 800 °C.

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We form carbon-doped n-BaSi2(0.35 μm)/p-Si(111) heterojunction diodes by radio-frequency sputtering using BaSi2 and SiC targets, and demonstrate the solar cell operation for the first time under AM1.5 illumination. The electron trap level was measured to be 0.21 eV below the conduction band edge of the n-BaSi2 layers by deep-level transient spectroscopy. The shunt resistance reflecting the quality of the heterointerface exceeds 0.7 MΩ, one order of magnitude higher than that obtained for the same structure grown by molecular beam epitaxy. The carrier transport properties are discussed based on the external quantum efficiency spectrum and the band alignment.

We grow As-doped BaSi2 epitaxial films by molecular beam epitaxy (MBE) with GaAs granules as an As source and investigated their electrical and optical properties by changing a substrate temperature (TS) and a crucible temperature of GaAs (TGaAs) during MBE. Secondary ion mass spectrometry revealed that the density of As atoms in BaSi2 films was surely changed by TGaAs.The full width at half-maximum evaluated by the x-ray ω-scan rocking curve measurement reached a minimum of 0.36 ° at TS = 600 °C. We investigated the TS dependence of electron concentration (n) and mobility by Hall measurement. n increased with decreasing TS and reached a maximum of 4.3 × 10 18 cm −3 . The photoresponsivity of the As-doped BaSi2 films was higher than that of undoped ones at the same bias voltage, probably thanks to the reduction of point defects by As doping.