Influence of interdiffusion processes on optical and structural properties of pseudomorphic In(0.35)Ga(0.65)As/GaAs multiple quantum well structures

Interdiffusion has been investigated in molecular-beam epitaxially (MBE)-grown, highly strained ln(ind 0.35)Ga(ind o.65)As/GaAs multiple quantum well (MQW) structures. Thermal intermixing and impurity-free interdiffusion (IFID) was induced via rapid thermal annealing (RTA) at temperatures between 700 and 950 øC using GaAs proximity caps and electron-beam evaporated Si02 cap layers, respectively. Both reduced photolurninescence (PL) linewidths and increased PL intensities were observed following interdiffusion-induced band-gap shifts ranging from 6 to 220 meV. PL microscopy (PLM) investigations were utilized to study the onset of strain relaxation due to dislocation generation. Two types of line defects were found in the proximity-cap annealed samples, depending on the annealing temperature and the number of QWs: misfit dislocations with the dislocation lines parallel to(110) directions and (100)-oriented line defects. No dislocations were observed in the Si02-cap, annealed samples over the entire temperature range investigated here. Resonant Raman scattering measurements of the 1LO/2LO phonon intensity ratio were used for a semiquantitative assessment of the total defect densities, including point defects (PDs). Whereas increasing PD densities and the formation of line defects were observed in the proximity-capped samples as the annealing temperature was increased, no deterioration of the structural quality due to an increased PD density was observed in the case of the Si02-cap annealed samples.