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.