Photoresponse properties of undoped BaSi₂epitaxial layers on n⁺-BaSi₂/p⁺-Si(001) by molecular beam epitaxy

Abstract

We investigated the photoresponse properties of 500-nm-thick undoped BaSi2 epitaxial layers formed on Sb-doped n+-BaSi2/p+-Si heterostructures by molecular beam epitaxy using Si(001) substrates. The external quantum efficiency (EQE) reached approximately 5% when 1 V was applied between the top and bottom electrodes. However, the EQE decreased to approximately 0.2% after inserting a solid-phase-epitaxy crystalline Si (c-Si) layer between the undoped and Sb-doped n+-BaSi2 layers to prevent Sb diffusion during the growth of the undoped BaSi2 overlayer. This result was unexpectedly different from that obtained for BaSi2 layers on Si(111), where the c-Si layer improved the EQE significantly.