Characterization of silicon(1-x)germanium(x)/silicon alloys and heterostructure devices

In this thesis, material and device characterizations are reported for Si{dollar}sb{lcub}1-x{rcub}{dollar}Ge{dollar}sb{lcub}x{rcub}{dollar} alloys and Si{dollar}sb{lcub}1-x{rcub}{dollar}Ge{dollar}sb{lcub}x{rcub}{dollar}/Si heterostructures. Among the characterizations transmission electron microscopy of the MBE grown Ge-rich heterostructures investigates the dislocation formation and propagation to identify an effective dislocation trapping buffer layer for device applications. SiGe/Si, p - i(Si{dollar}sb{lcub}1-x{rcub}{dollar}Ge{dollar}sb{lcub}x{rcub}{dollar}) - n photodiodes are designed, fabricated and characterized for the spectral response in the wavelength region of 0.6{dollar}mu{dollar}m to 1.6{dollar}mu{dollar}m. The cut-off wavelengths are presented for the entire composition range of 0.08 {dollar}le x le{dollar} 1. From photocurrent multiplication factors, the impact ionization coefficients, {dollar}alpha{dollar} and {dollar}beta{dollar} are measured for the first time in relaxed Si{dollar}sb{lcub}1-x{rcub}{dollar}Ge{dollar}sb{lcub}x{rcub}{dollar} alloys. The {dollar}beta/alpha{dollar} ratio, which is very important in the design of low noise avalanche photodiode, is reported as a function of Ge compositions as well. In addition, SiGe/Si heterojunction bipolar transistors are designed and fabricated by using a new selective wet chemical etchant of Si with respect to SiGe, tetramethyel ammonium hydroxide.; For the optical characterizations, the photoluminescence studies on SiGe/Si quantum structures and the measurement of electro-optic coefficients in Si{dollar}sb{lcub}1-x{rcub}{dollar}Ge{dollar}sb{lcub}x{rcub}{dollar} alloys are presented. Some enhancement in photoluminescence and the quantum confinement effect are observed in SiGe/Si multiquantum wells (MQW), disordered MQWs and disordered quantum wires. A large electro-optic effect in Si{dollar}sb{lcub}1-x{rcub}{dollar}Ge{dollar}sb{lcub}x{rcub}{dollar} and an attempt to measure this effect are reported by using Si{dollar}sb{lcub}1-x{rcub}{dollar}Ge{dollar}sb{lcub}x{rcub}{dollar}/Si ridge waveguides with asymmetric quantum wells in the active region.