Nucleation rate and glide velocity of misfit dislocations in Si1−xGex/(100) Si heterostructures

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Abstract
Expressions are presented for the rate of strain relaxation, misfit dislocation nucleation, and propagation in strained Si1−xGex/(100)Si heterostructures. Independent measurements of misfit dislocation nucleation and 60° type a/2 〈110〉 dislocation glide velocity in the temperature range 450–1000 °C have led to a model which characterizes the kinetics of strain relaxation for 0<xeff, which drives strain relaxation, is defined for an arbitrary strain profile and strained‐layer geometry. New experimental data for misfit dislocation glide velocity (V in cm s−1) have been fitted to a semi‐empirical relation found to be appropriate for all Si1−xGex/(100)Si heterostructures, V=(4±2)⋅1013(τeff /μ)2 exp−[(2.25±0.05)/kT]. An analogous expression for the nucleation rate of new misfit dislocation segments was determined from experimental data, dN(t)/dt=BN0(τeff /μ)2.5 exp−[2.5±0.2)/kT], where N0 is the density of heterogeneous nuclei and B is a material constant ∼1018 s−1 for Si1−xGex. These expressions are combined in a kinetic model which is then used to predict the rate of strain relaxation in Si1−xGex/Si heterostructures.