Dechanneling by misfit dislocations in III-V semiconductor heterostructures

This work reports on the use of the dechanneling technique for the determination of the misfit dislocation distribution at the interface between mismatched III-V semiconductor heterostructures grown on (001) substrates. Planar channeling is employed because of the higher sensitivity with respect to the axial case. For low misfit heterostructures, dislocations are oriented along the [110] and [110BAR] and the depth distribution is nearly planar and close to the chemical interface. We show that, for this kind of structure, dechanneling measurements allow one to determine the dislocation densities along the two quoted directions. This is done by using a fitting procedure based on a numerical simulation program of the RBS-channeling spectra. As a result of this procedure, an estimation of the dislocation distribution thickness can also be obtained, besides the ratio of the energy loss under channeling conditions to that under non-channeling conditions. Experimental data concerning a set of InxGa1-xAs/GaAs single layer samples having different thicknesses and indium concentrations are presented and discussed in the framework of this model. The dechanneling probability due to the misfit dislocations is obtained from the RBS-channeling spectra at several beam energies for all the samples. In some cases we note two distinct dechanneling probabilities for the two {110} channeling planes perpendicular to the interface. In light of the dechanneling cross section properties, this fact reflects the difference between the dislocation densities in the two directions.