Journal Article Evaluation of band offset at amorphous-Si/BaSi2 interfaces by hard x-ray photoelectron spectroscopy

Takabe, Ryota  ,  Takeuchi, Hiroki  ,  Du, Weijie  ,  Ito, Keita  ,  Toko, Kaoru  ,  Ueda, Shigenori  ,  Kimura, Akio  ,  Suemasu, Takashi

119 ( 16 )  , p.165304 , 2016-04 , American Institute of Physics
The 730 nm-thick undoped BaSi2 films capped with 5 nm-thick amorphous Si (a-Si) intended for solar cell applications were grown on Si(111) by molecular beam epitaxy. The valence band (VB) offset at the interface between the BaSi2 and the a-Si was measured by hard x-ray photoelectron spectroscopy to understand the carrier transport properties by the determination of the band offset at this heterointerface. We performed the depth-analysis by varying the take-off angle of photoelectrons as 15°, 30°, and 90° with respect to the sample surface to obtain the VB spectra of the BaSi2 and the a-Si separately. It was found that the barrier height of the a-Si for holes in the BaSi2 is approximately −0.2 eV, whereas the barrier height for electrons is approximately 0.6 eV. This result means that the holes generated in the BaSi2 layer under solar radiation could be selectively extracted through the a-Si/BaSi2 interface, promoting the carrier separation in the BaSi2 layer. We therefore conclude that the a-Si/BaSi2 interface is beneficial for BaSi2solar cells.

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