Influence of Ba-to-Si deposition rate ratios on the electrical and optical properties of B-doped BaSi₂ epitaxial films

Abstract

BaSi2 is considered a candidate for a light absorbing layer of a solar cell. The carrier type, carrier density, and photoresponsivity of undoped BaSi2 films depend on Ba-to-Si deposition rate ratios (RBa/RSi) during molecular beam epitaxy (MBE). In this study, we examined these properties of B-doped BaSi2 epitaxial films grown by MBE. We fabricated 0.5-µm-thick lightly B-doped BaSi2 epitaxial films on Si (111) substrates at a substrate temperature of 600 °C. RBa/RSi was varied in the range 1.0−5.6 and the B concentration was set at about 10 16 cm -3 . The p-type BaSi2 films were formed only in the range of RBa/RSi = 2.1−2.9, whereas BaSi2 formed with other values of RBa/RSi showed ntype conductivity. The photoresponsivity significantly depended on RBa/RSi, and reached values higher than those obtained for undoped BaSi2 films. We ascribed the enhancement of photoresponsivity to B atoms making Si vacancies inactive in B-doped BaSi2 films.

Comparison of C doping technique between SiC and C targets for high-photoresponsivity BaSi2 films by radio-frequency sputtering

“…8) Recently we supplied atomic hydrogen onto BaSi 2 films and greatly improved the carrier lifetime and photoresponsivity. [9][10][11] Similar results were also obtained in lightly B-doped 12) or As-doped BaSi 2 films, 13) wherein B and As atoms occupy Si sites and behave acceptors and donors, respectively. 2) We also demonstrated significant enhancement of photoresponsivity in C-doped BaSi 2 films formed by co-sputtering of BaSi 2 and SiC targets.…”

Atomic hydrogen passivation for photoresponsivity enhancement of boron-doped p-BaSi2 films and performance improvement of boron-doped p-BaSi2/n-Si heterojunction solar cells

“…Recent experiments have shown that lightly B-doped p-BaSi 2 films are more promising as a light absorbing layer than undoped ones. 28 We next discuss the effect of atomic H on the performance of p-BaSi 2 /n-Si solar cells.…”

Towards B-doped p-BaSi2 films on Si substrates by co-sputtering of BaSi2, Ba, and B-doped Si targets

“…It is noted that even B-doped BaSi 2 epitaxial films grown by MBE show n-type conductivity when the Ba/Si ratio in the BaSi 2 films departs from stoichiometry. 72) In this work, we explore another possibility, which is the effect of O atoms in BaSi 2 . Figure 4 shows the depth profiles of B and O atoms, and (Ba + Si) ion intensity in the as-grown samples fabricated by (a) sputtering and by (b) MBE.…”