Fabrication and Characterization of ZnO and GaN Devices for Electronic and Photonic Applications

Abstract

The research work presented in this dissertation is based on two direct and wide band gap semiconductors: ZnO and GaN. On the first part of the dissertation, the synthesis of ZnO nanorod array via the low temperature solution growth method on flexible In2O3-PET and rigid ITO-glass substrates were discussed. The analysis of the morphology, crystal quality, and optical property of ZnO nanorods synthesized with the solution growth process were investigated. Due to the high surface-to-volume ratio of ZnO nanorod, to alleviate the some of the drawbacks such as carrier mobility and thickness dilemma of organic solar cells, ZnO nanorod array were integrated into organic solar cells. In this ZnO nanorod array integrated bulk heterojunction organic solar cells, ZnO nanorods play an important role in rapid collecting and transporting charge carriers. Power conversion efficiency (η) of 1.8% is achieved in our ZnO nanorods integrated bulk heterojunction organic solar cells on flexible In2O3-PET substrates. On the second part of the dissertation, Aluminum gallium nitride/gallium nitride high electron mobility transistors (AlGaN/GaN HEMTs) were fabricated. RoundHEMT technology, which greatly simplifies the microelectronic fabrication process compared to traditional open fingers HEMT, was employed. Device testing and characterization under both room temperature and high temperature up to 300 °C were performed. The results show that the device can operate even at 300 °C with minimal degradation. Moreover, we propose a simple and novel spectroscopic photo I-V method of diagnosing the homogeneity of electrically-active defect distribution in the large area AlGaN/GaN HEMT epi structure grown on 6" silicon wafers.