Annealing effects on lattice-strain-relaxed In0.5Al0.5As/In0.5Ga0.5As heterostructures grown on GaAs substrates

High-temperature (600 degrees C) annealing, done to improve the electrical and optical qualities of lattice-strain-relaxed In0.5Al0.5As/In0.5Ga0.5As heterostructures grown on GaAs substrates at low temperatures, significantly improved the Hall mobilities of a n-In0.5Ga0.5As:Si layer, a n-In0.5Al0.5As:Si layer and a modulation-doped structure, but only slightly reduced sheet electron densities, if at all. This is in contrast to previous reports on fluorine termination of Si donors, which described significant degradation of electrical properties. The annealed single-quantum-well layer samples showed a photoluminescence intensity double that of the as-grown samples while maintaining the same line widths. These results suggest that the annealing did not increase the number of lattice-misfit dislocations, and transmission-electron microscopy and high-resolution photoluminescence microscopy confirmed this. (C) 1999 Elsevier Science B.V. All rights reserved.