Silicium germanium heterodevices

Silicium germanium (SiGe) is a completely miscible alloy with a lattice mismatch to the Si substrate of up to 4.17%. Accommodation of lattice mismatch f causes elastic strain ε, and/or misfit dislocations and surface corrugations. Onset of misfit dislocation generation takes place above a critical thickness tc which is dependant on mismatch and growth temperature. Critical thicknesses are compared for equilibrium models (Matthews-Blakeslee, > 750°C) with fit curves for 550°C growth experiments (People-Bean). The most important factors for successful silicon based heterodevices are analyzed, and as attractive areas for future research are defined; heterobipolar transistors (HBT) for high frequency communication, complementary heterojunction field effect transistors (HFET) for digital logic, 1.3 μm waveguide receivers for opto/microelectronics integration and self assembled quantum dot devices for multifunctional long term applications. Treatment of surface corrugations, adatom behaviour, surfactant phenomena and surface passivation of devices will be an essential part of future device oriented research.