Misfit Relaxation Research Articles

The Kinetics of Si1-xGex/Si Relaxation using Large Area Dislocation Imaging Techniques

AbstractAnnealing experiments in the 450-1000 °C temperature range on various MBE grown Si1-xGex/(100)Si heterostructures have revealed an abrupt thermally activated transition from coherently strained to partially relaxed microstructures. Misfit dislocations at densities 1 to 104 cm-2 have been monitored using Nomarski interference microscopy of defect etched surfaces and charge collection microscopy (EBIC) of Si1-xGex/Si heterojunctions in the scanning electron microscope. The kinetics of misfit relaxation by dislocation glide can be characterized by a relaxation temperature which for 30 minute furnace anneals was ~500 °C for an uncapped Si0.83Ge0.17 stramed layer, and ~600 °C for a similar buried strained layer typical of heterojunction bipolar transistor geometries. Rapid thermal anneals (5s) delayed the onset of relaxation to higher temperatures (~ 200 °C increase) and allowed misfit dislocation velocities to be determined for the temperature range 500-900 °C. The activation energy for dislocation glide was found to be 2.2±0.1eV for a Si0.9Ge0.1/Si strained layer superlattice, 1.6±0.2eV for a Si capped Si0.88Ge0.12 layer and 1.6±0.2eV for a Si0.83Ge0.17 uncapped strained layer.