We have successfully grown 360-nm-thick undoped n-BaSi2 epitaxial layers on the n(+)-BaSi2/p(+)-Si(111) tunnel junction, by molecular beam epitaxy. The external quantum efficiency reached approximately 17.8% at 500 nm under a reverse bias voltage of 4 V at room temperature, the highest value ever reported for semiconducting silicides. The quantum efficiency was compared to 240-nm-thick undoped n-BaSi2 epitaxial layers on a p-Si(111) substrate. (C) 2011 Elsevier B. V. All rights reserved.