Growth of GaAs epilayers on si substrate for high efficiency thin film solar cell application

Today, GaAs-based III-V group semiconductor solar cell technology based on epitaxial film lift -off (ELO) method, which allows the repeated use of GaAs substrates for sequential growth, draws a significant in photovoltaic area. While this cell technology minimizes the production cost of highly efficient III-V group cells, it offers a wide usage and widespread potential in many practical applications due to the functionalities brought by its flexibility and lightweightness. In this thesis, to make substantial decrease in GaAs based flexible thin film group III-V solar cell costs, these cell technologies have been aimed to developed over the matured and cheap Si substrates instead of over expensive GaAs substrates. Three different dislocation filters were designed and tested to achieve high quality heteroepitaxial growth on Si: Quantum dot, strained layer superlattice and growth at different temperature in thermal cycle. The designed flexible thin film GaAs solar cell structures were grown with these buffer layers on Si substrates using molecular beam epitaxial (MBE) system. Optical and structural characterizations of buffer layers and solar cell structures were performed before and after thin film lift-off process, and quality and defect density analysis of active cell epitaxial films were done. Using ELO method, flexible thin film GaAs solar cells were fabricated and tested for the first time over Si substrates