Strain relaxation and the resultant generation of defects was studied in GaAs/Ga1-xInxAs heterostructures, where x was between 0.05 and 0.3. They were prepared by means of metal-organic chemical vapour deposition, and were studied by using photoluminescence, positron beam and X-ray diffraction techniques. The photoluminescence data indicated peak shifts in, and broadening of, the spectra as the In concentration was increased. The broadening was attributed to defect generation which was caused by In substitution beyond the critical limit. Depth-resolved defect-sensitive S-parameter measurements, using a low-energy positron beam, revealed an increase in the S parameter over depths which corresponded to the In-substituted layers as the In concentration was increased. The results suggested that there was a production of open-volume defects, like misfit dislocations, in the In-substituted layer. An analysis of the positron-beam data showed that a 5%In sample was defect-free, thus indicating that it was pseudomorphic to the substrate. The 10%In sample was a borderline case, while higher In-concentration samples indicated the presence of a large concentration of defects. A combined study of the data from the above 3 techniques clearly established an interplay between In substitution, and strain relaxation leading to defect generation.

Study of Defects and Strain Relaxation in GaAs/InGaAs/GaAs Heterostructures using Photoluminescence, Positron Annihilation, and X-Ray Diffraction B.M.Arora, K.S.Chandrasekaran, M.R.Gokhale, G.Nair, G.V.Rao, G.Amarendra, B.Viswanathan: Journal of Applied Physics, 2000, 87[12], 8444-50