Characterization of CdTe Based Photodetectors, ZnO Nanowires and Nanostructures for Photonic Applications

With the constant drive for higher performance and new functionality in modern electrical and optical devices, the need for growth and characterization in a practical, economical and controlled manner has become increasingly important. The intent of my proposed research is to help provide a vertically-integrated basis of knowledge about such nanostructures, from basic materials science and physics to fabricate and characterize electronic and photonic devices. This work will have important technological applications ranging from detectors, sensors, solar cells, lasers, transistors and nanogenerators etc. The proposed research encompasses three distinct, but completely synergistic and overlapping categories. First part of my thesis involves analysis on the structural, vibrational and defect states of chlorine treated polycrystalline CdTe thin films. Cadmium telluride (CdTe) has been regarded as a promising semiconductor material for the detection of infrared (IR) radiations, hard X-rays, γ-rays and also in photovoltaics applications. An important limiting factor for device performance for these detectors are recombination and noise limitations. A method is proposed to study and optimize electrical and optical parameters of individual layers of CdTe/CdS based devices that can help tremendously improve the performance and thus enhance the overall efficiency of cells. Secondly successful fabrication of gold nano particles using properties of the block co polymer self-assembling into highly ordered and periodic nanodomain is achieved as compared to conventional lithography techniques. These materials can serve as templates for the vapor-liquid-solid (VLS) growth of semiconductor nanowires, whereas gold nanodots also possess attractive applications in optoelectronic devices, photonics and plasmonics applications. Lastly doping and band gap engineering of oxide based ZnO nanowires with indium (III) oxide is achieved using vapor liquid solid (VLS) technique and enhanced optical properties and detailed defect state analysis are reported. Complex ZnO nanostructures are fabricated and a detailed study of the optimized growth conditions of ZnO nanowires are presented. Further spontaneous polarization effects induced by these polar wurtzite nanowires are explored with applications including (but not limited to) solar cells, photodetectors, plasmonics, light emitters, nanogenerators, etc.