Dislocation blocking in InxGa1−xAs (x<0.20) layers grown on GaAs substrates revealed by strain sensitive etching with aqueous CrO3–HF solutions

Results from transmission electron microscopy (TEM), Nomarski interference microscopy and strain sensitive defect etching of epilayers with CrO3 are presented on single InxGa1−xAs (x<0.20) layers grown on GaAs substrates. The epilayer thickness in all the samples grown was significantly greater than the critical thickness (hc) defined by Matthews and Blakeslee [J. W. Matthews and A. E. Blakeslee, J. Cryst. Growth 27, 118 (1974)]. For these layers there should be a significant amount of relaxation with a high level of dislocation interaction observed at or near to the heteroepitaxial interface. It is shown that orthogonal dislocations, and in particular long 60° and edge dislocation segments lying in the epilayer above the interface play an important role in determining the mean free path of glissile 60° dislocations due to the action of large scale dislocation blocking. The level of dislocation blocking is significantly greater than that found by TEM observations. It is shown that etching with CrO3 is an effective method for revealing dislocation blocking over large areas of a wafer (in principle an entire wafer) and these interactions can be easily viewed using Nomarski interference microscopy.