MISFIT DISLOCATION PROPAGATION KINETICS IN GE(X)SI(1-X) GE(100) HETEROSTRUCTURES

We report measurements of misfit dislocation propagation velocities in GexSi1-x epilayers grown upon Ge(100) substrates, as opposed to the more usual Si(100) substrates. This geometry allows us to study structures with high Ge concentration (x greater-than-or-equal-to 0.8) and to compare with previous extensive measurements for lower Ge concentration layers (x less-than-or-equal-to 0.35) grown upon Si(100). It is found that all data are well described by a misfit dislocation velocity which is linear with excess stress, and which incorporates a compositionally dependent activation energy with linear interpolation between bulk values for Si and Ge. The combined data sets from structures grown on Si(100) and Ge(100) substrates is analyzed in the framework of the diffusive double kink model for dislocation motion.