Structural and electronic properties of GaAs/InGaAs/GaAs heterostructures

The authors present a study of GaAs/InGaAS/GaAs (001) strained layer heterostructures using transmission electron microscopy (TEM) as a structural tool to determine the misfit dislocation structure and density as a function of indium concentration. The average misfit dislocation spacing varies from > 10 μm for x < 0.3, to a few micros at x = 0.3, and drops to a few hundred angstroms at x = 0.5. They did in-situ annealing experiments in order to study the strain relaxation process, measuring the temperature at which the structure begins to relax and the dislocation velocities. Dislocation velocities are a few microns per second at the growth temperature of 450 degrees C, and tens of microns per second at 690 degrees C. In addition to interfacial dislocations in the usual left-angle 110 right-angle directions, in samples where x ≥ 0.4, the authors observed dislocations running in left-angle 100 right-angle directions. A study of the electrical characteristics of the material was made in parallel with the structural measurements