A Refined Model For Threading Dislocation Filtering In InxGa1−xAs/GaSAs Epitaxial Layers

Abstract

AbstractA model is presented for the filtering of threading dislocations in InxGa1−xAs/GaAs epitaxial single layers by accurate control of the layer thickness. The model developed differs from previous models since the InxGa1−xAs growth is restricted to less than ten times the Matthews and Blakeslee critical thickness (hc) where the asymmetry in the [110] and [110] dislocation densities is the greatest. Beyond this thickness it is shown that the removal or annihilation of threading dislocations (TDs) in the epilayer is more than offset by the introduction of new TDs from spiral and Frank-Read type sources. Results from strain sensitive etching with CrO3 aqueous solutions show that the TD density can be reduced by up to a factor of ten below that found in the substrate. Atomic force microscopy shows that these thin layers maintain a high level of surface quality with an absence of striations. Evidence is also shown that this type of defect etching is suitable for revealing large scale dislocation blocking in samples that have been grown significantly beyond 10hc.