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Fennessey, Tim

Materials Science Program

2006

M.S.

Research involving gallium antimonide (GaSb) has recently intensified due to applications in high-speed electronics such as terrahertz transistors as well as midrange infrared lasers, detectors, and thermophotovoltaic cells. A disadvantage of GaSb is the native defect in the lattice that results in an intrinsic p-type high carrier concentration, which puts very serious limits on the construction of GaSb-based devices. Another obstacle in the development of GaSb based devices is cost. As the price GaSb wafers remains high (>50 times the cost of silicon wafer), the growth of thin film GaSb on silicon substrates presents an economically viable process to introduce GaSb based devices. A proof of concept study was performed in the growth of thin film GaSb on a novel flexible substrate for the development of high mobility GaSb-based thin film transistor (TFT) devices. It has been suggested that doping with hydrogen will cure the native defect. The effect of hydrogen and deuterium on the heteroepitaxial growth of GaSb on silicon substrates is investigated in an effort to passivate this defect and reduce the intrinsic carrier concentration. Van der Pauw-Hall measurements show a change in cartier type from intrinsically p-type to n-type with the incorporation of deuterium. The use of a flexible substrate for the heteroepitaxial growth of a III-V semiconductor has largely been unexplored. Thin film GaSb was grown on a novel, high-temperature, flexible substrate known as Versalite. The highest hole mobility obtained is approximately 100 cm²/Vs, which is an order of magnitude greater than current TFT technology. The growth of thin film GaSb on silicon substrates may provide an economically feasible method to produce such devices by incorporating current silicon technology without relying on costly GaSb substrates. This thesis explores the problems of reducing the intrinsic carrier concentration and as well as the development of novel high speed TFTs.