Integration of III-Vs on silicon: from the micron to the nanometre regime

点击翻译按钮获取中文摘要

During decades the complexity of silicon CMOS technology has continuously been increasing, driven by ever rising demands for higher speed and storage capacity. For the most part, these demands could be met by breath taking advances in miniaturization to a degree unthinkable a generation ago. Lately, however, in view of concerns about power consumption, data transmission, and new applications in hitherto inaccessible fields, additional functionalities are becoming more and more urgently needed. New functionalities necessarily imply silicon technology to be extended to other semiconducting materials with optical and electrical properties beyond those of Si alone.In view of its excellent optical and electrical properties GaAs is one of the most important III-V semi-conductors. It is the goal of this project to explore the epitaxial growth by metal organic chemical va-pour deposition (MOCVD) of semiconductor stacks based on GaAs on patterned Si and Ge/Si sub-strates. This will be the first necessary step towards the monolithic integration of elementary optical-device subcomponents, such as waveguides, grating couplers and lasers on a Si CMOS platform. The challenge here is to overcome the problem of crystal defects arising from the large mismatch of lattice parameters and thermal properties which has so far hindered GaAs-on-Si technology to be applied. In our approach the epitaxy will be carried out on specially designed substrate patterns with large aspect ratios and lateral dimensions ranging from several microns to tens of nanometers. This will permit to explore the evolution of dislocation structures anti-phase domains as a function of the pattern size, which defines the transition from an essentially rigid to a compliant substrate regime. The substrate patterning will include sidewall passivation of the etched Si features, permitting the use of selective epitaxy techniques for precise positioning of the compound semiconductor stacks either directly on Si or on selectively grown Ge buffer structures.The relation between pattern geometry and defect structure will be studied by structural, analytical and optical techniques, such as transmission electron microscopy (TEM), atom probe measurements, high-resolution X-ray diffraction (HR-XRD) including synchrotron nanodiffraction, micro-Raman and photoluminescence spectroscopy. We intend to design special test structures in order to prove the device quality of epitaxial III-V material on mismatched Si substrates. These will permit to assess lasing action by optical pumping as a preliminary step towards the fabrication of monolithically integrated lasers on CMOS-processed Si-wafers.