Strain mapping in [111] and [001] InGaAs/GaAs superlattices

Raman area maps measuring the strain in lattice-mismatched [111] and [001] oriented InxGa1−xAs/GaAs superlattices (x=0.1, 0.17) are presented and compared with independent x-ray rocking curve studies of the average strain in the same samples. We find that the LO phonon frequency, but not the TO frequency, is a valid measure of strain for [111] oriented superlattices exhibiting one-mode behavior. This is explained by the lack of compensation between the effects of alloying and strain for the TO mode in InxGa1−xAs. The capability to nondestructively map small growth variations in superlattice and buffer layer constituents is demonstrated.