Depth Dependent Defect Analysis in R.B.S./Channeling.

Rutherford backscattering combined with channeling is used as a measure of the crystalline quality of thin films. For lattice mismatched structures the channeling spectrum implicitly contains the quantitative depth distribution of dislocation defects through a deconvolution analysis that takes into account the rate of dechanneling with depth. We describe a sputtering/depth profiling procedure to extract the defect density which tests this deconvolution procedure to extract the depth profile. It is shown that the analysis can severely underestimate the defect density at large depths. This discrepancy can be resolved, however, when energy loss straggling is taken in account as we show by further analysis. These procedures are applied to the important system of GaAs grown onto Si.