STRAIN RELIEF STUDY CONCERNING THE INXGA1-XAS/GAAS (0.07-LESS-THAN-X-LESS-THAN-0.5) MATERIAL SYSTEM

The evolution of dislocations in the InxGa1-xAs/GaAs material system has been studied as a function of the ternary alloy comparison in the range 0.07 < x < 0.5. Cross-sectional transmission electron microscope observations indicate that for x < 0.18, threading dislocations are absent in the epilayer and dislocations propagate from the heterointerface into the GaAs material, while, for 0.18 < x < 0.28, all dislocations appear to propagate into both the epilayer and the GaAs. Furthermore, for x > 0.28, all the dislocations are observed in the epilayer while the GaAs appears to be dislocation-free. We propose a model involving the balance of forces acting on misfit dislocations generated at the heterointerface which includes a surface image force term to explain our observations of dislocation evolution as a function of the ternary alloy composition.