Growth and Characterization of Polycrystalline Indium Phosphide on Silicon

Abstract: III-V thin film solar cells attract large interest among the scientific community as a highly efficient solar energy source. High cost of the III-V materials, however, is the fundamental limitation for using these materials as a household energy source. Integrating these materials on low cost and large area Si wafer both for photovoltaic and photonics application is a field of research that draw intense attention of the scientific community. The fundamental challenge to fabricate III-V materials directly on silicon wafers arises from the disparity in polarity, large lattice and thermal mismatch between the III-V semiconductors and Si. In this work, we introduce a method to synthesize polycrystalline InP directly on silicon wafer by using In2O3 or In as intermediate material. The crystal quality and conversion degree of the intermediate material and the final poly-InP were analyzed by Powder X-ray Diffraction. Depending on the type of the intermediate material and substrate orientation (Si (100) or Si (111)), the crystallite size was found to be varying from 739 to 887 nm. The surface morphology of poly-InP was studied by using Atomic Force Microscopy. The root mean square surface roughness of the InP thin film was found to be varying from 314 to 1944 nm. Structural and optical qualities of intrinsic and sulfur doped InP layers were compared at different growth conditions (growth time, growth temperature, PH 3 source flow), intermediate material type(In2O3 and In) and substrate type (Si (100) and Si (111)). Within the investigated experimental parameter range, the higher PH 3 source flow at longer growth time improved the structural quality of InP layer grown on In 2O3 coated on silicon substrate, which also result in good optical quality. Comparison of structural and optical qualities of InP grown from In and indium oxide precoated substrates show that the former gave better quality InP. These achievements will be helpful in the realization of the high efficiency III-V solar cell on silicon substrate as a low cost option.