著者

Toko Kaoru Fukata Naoki Nakazawa Koki Kurosawa Masashi Usami Noritaka Miyao Masanobu Suemasu Takashi

出版者

Elsevier B.V.

雑誌

Journal of crystal growth (ISSN:00220248)

巻号頁・発行日

vol.372, pp.189-192, 2013-06

被引用文献数

15 4

---

High-quality crystalline Ge thin films on low-cost glass substrates are desired to reduce the fabrication cost of high-efficiency tandem solar cells. We applied an Al-induced crystallization technique to amorphous-Ge films (50-nm thickness) on SiO2 glass substrates. The annealing temperature of the sample strongly influenced the grain size and the crystal orientation in the grown polycrystalline Ge layers: low annealing temperatures resulted in large grains and high (111)-orientation fractions. As a result, annealing at 325 °C provided 98% (111)-oriented grains with average diameters of 30 μm. Moreover, the grown Ge layers could be used as an epitaxial template for chemical vapor deposition. This large-grained Ge film on a SiO2 substrate appears promising for use as a Ge light-absorbing layer, as well as an epitaxial buffer layer for group III–V compound semiconductors.

著者

Murakami Kouichi Shirakawa Ryota Tsujimura Masatoshi Uchida Noriyuki Fukata Naoki Hishita Shun-ichi

出版者

American Institute of Physics

雑誌

Journal of applied physics (ISSN:00218979)

巻号頁・発行日

vol.105, no.5, pp.054307, 2009-03

被引用文献数

22 11

---

We have investigated phosphorus ion (P+) implantation in Si nanocrystals (SiNCs) embedded in SiO2, in order to clarify the P donor doping effects for photoluminescence (PL) of SiNCs in wide P concentrations ranging in three orders. Some types of defects such as Pb centers were found to remain significantly at the interfaces between SiNCs and the surrounding SiO2 even by high-temperature (1000 °C) annealing of all the samples. Hydrogen atom treatment (HAT) method can efficiently passivate remaining interface defects, leading to significant increase in the intensity of PL arising from the recombination of electron-hole pairs confined in SiNCs, in addition to significant decrease in interface defects with dangling bonds detected by electron spin resonance. From both the results of the P dose dependence before and after HAT, it is found that the amount of remaining defects is higher for samples with SiNCs damaged by implantation with relatively lower P+ doses and then annealed, and that through HAT the observed PL intensity increases surely as the P concentration increases up to a critical concentration. Then it begins to decrease due to Auger nonradiative recombination above the critical concentration which depends on the size of SiNCs. These results suggest an effect of relatively low concentration of P atoms for the enhancement of PL intensity of SiNCs and we present an unconventional idea for explaining it.

著者

Uchida Noriyuki Mikami Youhei Kintoh Hiroshi Murakami Kouichi Fukata Naoki Mitome Masanori Hase Muneaki Kitajima Masahiro

出版者

American Institute of Physics

雑誌

Applied physics letters (ISSN:00036951)

巻号頁・発行日

vol.92, no.15, pp.153112, 2008-04

被引用文献数

5

---

We have developed a robust method for fabricating Si nanoregions in silica glass using femtosecond laser processing. We attained a vivid formation of silicon-rich nanoregions site-selectively generated in SiO2 by irradiation of femtosecond laser pulses to the interface of a SiO2 substrate and deposited aluminum (Al) thin film, where the Al element acts as a gettering site for O atoms. Growth of high-density Si nanocrystals and amorphous Si was observed by transmission electron microscopy in the region that was multiply irradiated with the femtosecond laser. Furthermore, local annealing with a cw laser enhances the Si nanocrystal growth, which was determined by micro-Raman measurements.