Improved internal quantum efficiency in high-quality BaSi2 films grown by molecular beam epitaxy

• Main Authors: Weijie Du, Suzuno, M., Khan, M. A., Toh, K., Baba, M., Nakamura, K., Toko, K., Usami, N., Suemasu, T.
• Format: Conference Proceeding
• Language: English
• Subjects: Atomic layer deposition; Barium; BaSi2; Internal quantum efficiency; Molecular beam epitaxial growth; Photoresponsivity; Silicon; Solid phase epitaxy; Substrates
• ISSN: 0160-8371
• DOI: 10.1109/PVSC.2012.6317815

A new method has been developed for the formation of undoped BaSi 2 absorption layers on an Sb-doped n + -BaSi 2 /p + -Si tunnel junction (TJ) formed on Si(111). The diffusion of Sb atoms from the n + -BaSi 2 layer was effectively suppressed by inserting a thin Si layer between the n + -BaSi 2 and 400-nm-thick undoped BaSi 2 layers. The inserted Si layer was firstly deposited at room temperature, followed by annealing at 650°C by solid phase epitaxy (SPE). Both X-ray diffraction (XRD) and reflection high-energy electron diffraction (RHEED) patterns indicated the good crystalline quality of undoped BaSi 2 overlayers; the I-V characteristics revealed the excellent tunneling effect of the TJ. The photoresponsivity has been greatly improved by the new growth method and reached a maximum of 0.37 A/W at 1.55 eV under a bias voltage of 2 V; the corresponding external quantum efficiency (EQE) and internal quantum efficiency (IQE) increased up to 60% and 70%, respectively, which is the highest value ever reported for semiconducting silicides.