Cross-sectional electric field distributions in BaSi2 homo and BaSi2/Si hetero pn junctions

Electrical field distributions at the interfaces of p-type and n-type BaSi₂ homo junction and n-type BaSi₂ and p-type Si heterojunction were evaluated by electron beam induced current (EBIC) technique. It was confirmed from transmission-electron microscopy that p-BaSi₂ and n-BaSi₂ layer were clearly separated. For the n-BaSi₂/p-Si hetero junction, we observed strong electric field at the interface. We consider that the large difference in work function between BaSi₂ and Si contributes to this result. On the other hand, for the BaSi₂ pn junction, smaller electric field than that at the BaSi₂/Si hetero interface was observed. We assumed that heavily B-doped p-BaSi₂ was not formed due to not sufficient activation of boron, leading to the smaller electric field than expected. In both cases, the observation of the electric field means that the pn junction was formed at the BaSi₂ homo and BaSi₂/Si hetero interfaces. Therefore, we succeeded in forming a BaSi₂ pn junction; however higher built-in potential is necessary at the junction to achieve high efficiency BaSi₂ solar cells.