Effect of Ge Interlayers on Threading Dislocation Behavior in GaAs on Si

Threading dislocation morphologies and characteristics have been investigated in 3 μm thick GaAs films with Ge interlayers having various thicknesses above and below the critical thicknesses (h_c) for dislocation generation in Ge on GaAs grown by molecular beam epitaxy on tilted (3° toward [110]) Si (001) substrates using cross sectional transmission electron microscopy. In as-grown samples the running direction of most of the dislocations changes at the lower Ge/GaAs interfaces. However, almost all of the dislocations in the Ge interlayers thread into the upper GaAs films, with no particular change in the running direction at the upper GaAs/Ge interfaces. After annealing at 800 °C for 30 min, the interactions of the dislocations with the interlayers are pronounced in all of the samples, resulting in the enhancement of bent dislocations at the interfaces of both Ge/GaAs and GaAs/Ge. However, in a sample having a 9500 Å thick Ge layer far above h_c, a high density of antiphase domains (APDs) remains in the GaAs film on Ge even after annealing. Interactions of the APDs with the dislocations are observed.