OBSERVATIONS OF NEW MISFIT DISLOCATION CONFIGURATIONS AND SLIP SYSTEMS AT ULTRAHIGH STRESSES IN THE (AL)GAAS/INXGA1-XAS/GAAS(100) SYSTEM

We have observed new misfit dislocation configurations and slip systems in (Al)GaAs/InxGa1-xAs/GaAs(100) heterostructures for x greater-than-or-equal-to 0.4. Dislocations are observed running along [001] directions in the interface, which are inconsistent with conventional glide of misfit dislocations on {111} planes in the zincblende lattice. Diffraction contrast analysis in a transmission electron microscope (TEM) shows that these dislocations are of the edge type with b = a/2[011], inclined at 45-degrees to the interface. In situ TEM heating experiments reveal dislocation propagation velocities approximately tens of mu-m s-1 at 600-degrees-C, suggesting that they are moving by glide, rather than climb. The only slip planes consistent with these observations are {110} planes inclined to the interface. This represents a new relaxation mechanism in highly strained semiconductor heterostructures.