著者

Hara K. O. Usami N. Toh K. Baba M. Toko K. Suemasu T.

出版者

American Institute of Physics

雑誌

Journal of applied physics (ISSN:00218979)

巻号頁・発行日

vol.112, no.08, pp.083108, 2012-10

被引用文献数

83

---

Excess-carrier recombination mechanisms in undoped BaSi2 epitaxial films grown by molecular beam epitaxy on n-type silicon substrates have been studied by the microwave-detected photoconductivity decay measurement. The measured excess-carrier decay is multiexponential, and we divided it into three parts in terms of the decay rate. Measurement with various excitation laser intensities indicates that initial rapid decay is due to Auger recombination, while the second decay mode with approximately constant decay to Shockley-Read-Hall recombination. Slow decay of the third decay mode is attributed to the carrier trapping effect. To analyze Shockley-Read-Hall recombination, the formulae are developed to calculate the effective lifetime (time constant of decay) from average carrier concentration. The measurement on the films with the thickness of 50–600 nm shows that the decay due to Shockley-Read-Hall recombination is the slower in the thicker films, which is consistent with the formulae. By fitting the calculated effective lifetime to experimental ones, the recombination probability is extracted. The recombination probability is found to be positively correlated with the full width at half-maximum of the X-ray rocking curves, suggesting that dislocations are acting as recombination centers.

著者

Baba M. Toh K. Toko K. Hara K.O. Usami N. Saito N. Yoshizawa N. Suemasu T.

出版者

Elsevier B.V.

雑誌

Journal of crystal growth (ISSN:00220248)

巻号頁・発行日

vol.378, pp.193-197, 2013-09

被引用文献数

5 1

---

BaSi2 epitaxial films were grown on Si(111) substrates by a two-step growth method including reactive deposition epitaxy (RDE) and molecular beam epitaxy (MBE). To enlarge the grain size of BaSi2, the Ba deposition rate and duration were varied from 0.25 to 1.0 nm/min and from 5 to 120 min during RDE, respectively. The effect of post-annealing was also investigated at 760 °C for 10 min. Plan-view transmission electron micrographs indicated that the grain size in the MBE-grown BaSi2 was significantly increased up to approximately 4.0 μm, which is much larger than 0.2 μm, reported previously.

著者

Nakamura K. Toh K. Baba M. Khan M. Ajmal Du W. Toko K. Suemasu T.

出版者

Elsevier B.V.

雑誌

Journal of crystal growth (ISSN:00220248)

巻号頁・発行日

vol.378, pp.189-192, 2013-09

被引用文献数

9 4

---

Al or B layers of a few hundreds of nm in thickness deposited on BaSi2 epitaxial films on Si(1 1 1) substrates were annealed at different temperatures, and the diffusion coefficients of Al and B were evaluated using secondary ion mass spectrometry with O2+. We also investigated the effect of post annealing (850 °C, 10 min) of BaSi2 films on the diffusion coefficients. It was found that both the lattice diffusion and the grain boundary diffusion were decreased by the post-annealing. The plan-view transmission electron microscopy images revealed that the grain size was increased from approximately 0.2 to 0.6 μm by the annealing, and the X-ray diffraction intensities also increased. The activation energies of lattice and grain boundary diffusions in the post-annealed BaSi2 are 0.63 eV and 0.58 eV for Al, and 4.6 eV and 4.4 eV for B, respectively.