Journal of Nanomedicine & Nanotechnology

Subband formation in multi stacked InGaAs quantum dots with different interdot spacing for high efficient solar cell

2^nd International Conference on Nanotek and Expo

December 3-5, 2012 DoubleTree by Hilton Philadelphia Center City, USA

K. Goshima, N. Tsuda, J. Yamada, K. Komori and T. Sugaya

Scientific Tracks Abstracts: J Nanomed Nanotechol

Abstract:

Quantum dots (QDs) have been attractive candidate for optical device such as a solar cell medium. The multi-stacked QDs are not only the higher optical gain, but also a potential to realize subband formation, which is important technology for a high efficient solar cell. We investigated the subband formation in multi-stacked QDs with diiferent interdot spacing. Self- organized In 0.4 Ga 0.6 As multi-stacked QDs were grown on a Si-doped GaAs(001) substrate using As2 sources. We grew 20-stack In 0.4 Ga 0.6 As QD structures with interdot spacing of 3.5 and 15nm. Height, width and shape of a dot are 5nm, 20nm and pyramidal, respectively. We calculated the subband formation with various interdot spacing. To compute the electronic states taken on by quantum dot embedded in the GaAs surrounding, we solved the Schr?dinger equation in the effective mass approximation using the 3-dimension finite element modeling. We expected that the subband formation is created by interdot spacing under 10nm. We conducted a detailed investigation of the subband formation and electronic structures within multi-stacked QDs using three independent experimental techniques: the power dependence of photoluminescence (PL) spectroscopy, PL excitation (PLE) spectroscopy and time-resolved PL spectroscopy. We observed different behaviors with respect to interdot spacing of 15nm and 3.5nm. These results offer an existence of the subband formation in the multi stacked QDs. By employing a theory and experiments, we obtained the detailed subband formation in multi stacked QDs with regard to different interdot spacing

Biography :

K.Goshima has completed a Ph.D. from Aichi Institute of Technology (AIT) and postdoctoral studies from the Ultrafast Optoelectronic Device Group, Photonics Research Center, National Institute of Advance Industrial Science and Technology (AIST), Japan. During 2008-2010, he joined the Department of Reliability-based Information System engineering, Kagawa University, Japan. In 2011, he joined the Electrical and Electronics Engineering, Aichi Institute of Technology, Japan, as an assistant professor. His current research interests include optical devices using quantum dots