Vertical and Tilted III-V Semiconductor Nanowires on Silicon for PV Application
G. Radhakrishnan, A. Freundlich, A. Alemu, B. Fuhrmann
Center for advanced materials, US
Keywords: nanowires, solar cell, III-V
Abstract:The key to a successful quantum-confined solar cell is to develop a design of the intrinsic region that will allow a rapid transfer of the photoconverted carriers to the conventional p and nconductivity regions. We expect this requirement to be satisfied in the vertical quantum wire (VQW) solar cells, where a vertical array of nanometric wires (or vertical closely coupled dots) is inserted between the p and n conductivity regions of conventional solar cell. In such a device the presence of a one dimensional electron gas across the junction region will result in a fast collection of the carriers photo-generated in the nanowires region, and the solar cell output will thus fully benefit. This unique capability of nanowires to transfer photo-generated carriers across a photovoltaic device has lead to our interest in the fabrication of nanowires. This work demonstrates the growth of GaAs and InP nanowires on Si(111) substrates using chemical beam epitaxy. To utilize the VLS (Vapour Liquid Solid) growth mechanism of nanowires, a uniform pattern of gold nanodots was deposited on the silicon substrate by using self assembled polystyrene nanospheres as a mask. The size of the gold dot ranged from 40nm to 150nm with a pitch of about 500nm. The growth was performed by chemical beam epitaxy(CBE) in a vapour phase environment. After growth the samples were characterized using Scanning electron microscopy, photoluminescence and X-ray diffraction spectroscopy. The nanowires were found to exhibit good photoluminescence and high crystalline quality paving way for potentially high efficiency photovoltaic applications.