Misfit dislocation injection, interfacial stability and photonic properties of Si-Ge strained layers

Abstract

Low temperature epitaxy permits the growth of highly strained Si1−xGex/Si multilayers. These exhibit unique optical and electrical properties characteristic of the alloy composition, the tetragonal distortion of the crystal lattice and the periodicity in the growth direction. The kinetics of strain relaxation; misfit dislocation nucleation and propagation for a range of thermal cycles, typical of Si-based device processing, are defined. The early stages of relaxation are characterized using an empirical kinetic model. The interface perfection, interdiffusion and segregation effects in Si1−xGex/Si multilayers are investigated using X-ray scattering techniques. Photoluminescence properties of Si1−xGex quantum wells and alloys, epitaxially deposited on Si are reviewed. Comparison is made between the sharp, near band edge luminescence typical of narrow Si1−xGex quantum wells and the transition to an intense ~ 80 meV broad PL peak obtained from thicker Si1−xGex epitaxial layers. The impact of interfacial roughening during epitaxy on PL character, and the quenching of luminescence due to misfit dislocation injection, are discussed.