Epitaxial Growth Of Si Ge Sn Alloys For Optoelectronic Device Application

Microelectronics industry has experienced a tremendous change over the last few decades and has shown that Moore's law has been followed by doubling the number of transistors on the chip every 18 months. However, continuous scaling down of the transistors size is reaching the physical limits and data transfer through metal interconnects will not be able to catch up with the increasing data processing speed in the future. Therefore, optical data transfer between chips and on-chip has been widely investigated. Silicon based optoelectronics has received phenomenal attention since Si has been the core material on which microelectronic industry has been built. However, due to the indirect bandgap nature of Si, its optical characteristics fall short compared to similar III-IV semiconductors. The efforts in III-V incorporation on Si substrate have not been successful due to the incompatibility of the growth with complementary metal oxide semiconductor processing. Germanium has been studied in order to develop a Si compatible technology and it has been shown that a direct bandgap material is achievable by alloying Sn in Ge. Further investigations on Si-Ge-Sn material system showed its viability as a technology that can be used for fabrication of Si-compatible light source and detectors. The work presented in this dissertation is focused on the low temperature growth of Si-Ge-Sn alloys. High quality crystalline homoepitaxial silicon films were deposited at 250 °C using a plasma-enhanced chemical vapor deposition (PECVD) system. Strain-relaxed Ge and SiGe films were also grown on Si substrate at 350-550 °C in a reduced pressure CVD system. Commercial precursors of silane and germane were used to grow the films at different chamber pressures. Germanium-tin and silicon-germanium-tin alloys were grown by a cold-wall chemical vapor deposition system at low temperatures (300-450 °C) directly on Si substrates. Two different delivery systems were adopted for the delivery of stannic chloride and deuterated stannane as Sn precursors along with silane and germane. Crystallinity and growth quality of the films were investigated through material characterization methods including X-ray diffraction, scanning electron microscopy and transmission electron microscopy. Elemental characterization of the films was done using Rutherford backscattering measurement and energy-dispersive X-ray spectroscopy. Moreover, optical characterizations were performed using Raman spectroscopy and photoluminescence on the samples to investigate Sn incorporation in the films. Additionally, compressively strained (