| AVS 62nd International Symposium & Exhibition | |
| Electronic Materials and Processing | Thursday Sessions |
| Session EM+EN-ThA |
| Session: | Materials for Light Management |
| Presenter: | Marina Nakano, Univ. of Miyazaki, Japan |
| Authors: | M. Nakano, Univ. of Miyazaki, Japan K. Sugihara, Univ. of Miyazaki, Japan D. Ohori, Univ. of Miyazaki, Japan K. Sakai, Univ. of Miyazaki, Japan H. Amano, Univ. of Nagoya, Japan Y. Honda, Univ. of Nagoya, Japan T. Ikari, Univ. of Miyazaki, Japan A. Fukuyama, Univ. of Miyazaki, Japan |
| Correspondent: | Click to Email |
GaAs nanowires (NWs) are expected to applying to optoelectronic devices. However, material properties have not been understood yet due to a presence of impurity and defect level related to an involved catalyst which was inevitable for growing nanowires. Recently, we succeeded in fabricating the catalyst-free GaAs NWs on a (111) Si substrates using a combination of molecular beam epitaxy and vapor-liquid-solid method [1]. The NW had two kinds of crystalline phases, a zinc-blend (ZB) and a wurtzite (WZ) structures [2]. We found the amount of WZ phase increased with increasing the amount of Si-doping by using high-resolution X-ray diffraction and transmission electron microscope [3]. In this study, we investigate the electronic band structure of Si-doped GaAs NWs by using a photoreflectance (PR) and a photoluminescence (PL) techniques and discuss the effect of Si-doping on the optical properties.
Three kinds of samples with different Si cell temperatures at 1015, 1065, and 1150ºC were grown. The average diameter and length of NWs were 60 nm and 35 mm, respectively. The amount of Si doping was evaluated by a carrier concentration estimated from a Hall measurement. The lowest hole concentration was 5.5 ×1017 cm-3 for the sample grown at 1015 ºc and increased about an order by increasing the cell temperature. PR and the PL emission light were carried at 4 K.
The crystallographic investigations showed that the amount of secondary WZ phase increased with increasing the Si-doping. Three critical energies were observed at 1.51, 1.49 and 1.43 Ev in the PR. The first two signals were observed for all samples and attributed to band to band and band to Si acceptor transitions, respectively. Since the signal at 1.43 Ev appeared only in high Si-doping sample with high amount of WZ phases, this is due to the band to band transition at the interface between the two different crystalline phases. In the PL spectra, three other emission peaks were observed at 1.46, 1.42 and 1.37eV. The intensities of these peaks changed for the samples with different cell temperature, these may be due to impurity and defect levels in nanowires. Si dopant itself as well as different crystal structure affect the electron transition. Since the interface transition observed at 1.43 Ev becomes dominant, emissions through such impurities were hidden for the sample with highest Si-doping. Temperature dependences of the PR and PL spectra will be discussed for further understanding the effect of Si-doping.
[1] J. H. Paek et al., Phys. Stat. Sol. (c) 6, 1436 (2009).
[2] D. Spirkoska et al., Phys. Rev. B 80, 245325 (2009).
[3] A. Suzuki et al., Jpn. J. Appl. Phys. 54, 035001 (2015).