DECHANNELING CROSS-SECTION FOR MISFIT DISLOCATIONS

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. In this case the dislocations are oriented along the [110] and [110BAR] and the depth distribution is nearly planar and close to the chemical interface. The displacement field caused by one misfit dislocation is calculated in the frame of the linear elasticity theory. An analytical treatment of the dechanneling cross section dependence on both the dislocation line and Burgers vector orientation and on the beam direction in the channeling plane is performed within the Quere model. It is shown that (110) planar channeling is most sensitive to the dislocation orientation. Experimental data concerning a set of InxGa1-xAs/GaAs single layer samples are presented and analyzed. The two {110} planes perpendicular to the interface show distinct dechanneling probabilities. In the light of the dechanneling cross section properties this fact reflects the difference between the dislocation densities in the two directions. The obtained dislocation densities are in agreement with those derived indirectly from strain measurements. It is shown that the sensitivity of the dechanneling technique is of the order of 10(4) dislocation lines cm-1.