2 0 0 0 OA Investigation of the recombination mechanism of excess carriers in undoped BaSi2 films on silicon
- 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
- Nakazawa K. Toko K. Saitoh N. Yoshizawa N. Usami N. Suemasu T.
- 出版者
- Electrochemical Society
- 雑誌
- ECS journal of solid state science and technology (ISSN:21628769)
- 巻号頁・発行日
- vol.2, no.11, pp.Q195-Q199, 2013-08
- 被引用文献数
- 17
Low-temperature (350°C) crystallization of amorphous Ge films on SiO2 was investigated using Al-induced layer exchange (ALILE) process. Thicknesses of Ge and catalytic Al layers were varied in the range of 30–300 nm, which strongly influenced the ALILE growth morphology. Based on the study, the Ge thickness was adjusted to 40 nm while the Al thickness was adjusted 50 nm. This sample satisfied both of the surface coverage of polycrystalline-Ge and the annihilation of randomly oriented Ge regions. Moreover, the enhancement of the heterogeneous Ge nucleation improved the (111) orientation and the grain size. As a result, the area fraction of the (111)-orientation reached as high as 97% and the average grain size as large as 70-μm diameters. This (111)-oriented Ge layer with large-grains promises to be the high-quality epitaxial template for various functional materials to achieve next-generation devices.
1 0 0 0 OA Formation of large-grain-sized BaSi2 epitaxial layers grown on Si(111) by molecular beam epitaxy
- 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. Baba M. Ajmal Khan M. Du W. Sasase M. Hara K. O. Usami N. 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.113, no.5, pp.053511, 2013-02
- 被引用文献数
- 21 11
A 180-nm-thick boron (B) layer was deposited on a 300-nm-thick a-axis-oriented BaSi2 epitaxial film grown by molecular beam epitaxy on Si(111) and was annealed at different temperatures in ultrahigh vacuum. The depth profiles of B were investigated using secondary ion mass spectrometry (SIMS) with O2+, and the diffusion coefficients of B were evaluated. The B profiles were reproduced well by taking both the lattice and the grain boundary (GB) diffusions into consideration. The cross-sectional transmission electron microscopy (TEM) image revealed that the GBs of the BaSi2 film were very sharp and normal to the sample surface. The plan-view TEM image exhibited that the grain size of the BaSi2 film was approximately 0.6 μm. The temperature dependence of lattice and GB diffusion coefficients was derived from the SIMS profiles, and their activation energies were found to be 4.6 eV and 4.4 eV, respectively.
- 著者
- Khan M. Ajmal Hara K. O. Du W. Baba M. Nakamura K. Suzuno M. Toko K. Usami N. Suemasu T.
- 出版者
- American Institute of Physics
- 雑誌
- Applied physics letters (ISSN:00036951)
- 巻号頁・発行日
- vol.102, no.11, pp.112107, 2013-03
- 被引用文献数
- 72 15
B-doped p-BaSi2 layer growth by molecular beam epitaxy and the influence of rapid thermal annealing (RTA) on hole concentrations were presented. The hole concentration was controlled in the range between 1017 and 1020 cm−3 at room temperature by changing the temperature of the B Knudsen cell crucible. The acceptor level of the B atoms was estimated to be approximately 23 meV. High hole concentrations exceeding 1 × 1020 cm−3 were achieved via dopant activation using RTA at 800 °C in Ar. The activation efficiency was increased up to 10%.
- 著者
- Toko K. Kurosawa M. Saitoh N. Yoshizawa N. Usami N. Miyao M. Suemasu T.
- 出版者
- American Institute of Physics
- 雑誌
- Applied physics letters (ISSN:00036951)
- 巻号頁・発行日
- vol.101, no.7, pp.072106, 2012-08
- 被引用文献数
- 88 20
(111)-oriented Ge thin films on insulators are essential for advanced electronics and photovoltaic applications. We investigate Al-induced crystallization of amorphous-Ge films (50-nm thickness) on insulators focusing on the annealing temperature and the diffusion controlling process between Ge and Al. The (111)-orientation fraction of the grown Ge layer reaches as high as 99% by combining the low-temperature annealing (325 °C) and the native-oxidized Al (AlOx) diffusion-control layer. Moreover, the transmission electron microscopy reveals the absence of defects on the Ge surface. This (111)-oriented Ge on insulators promises to be the high-quality epitaxial template for various functional materials to achieve next-generation devices.