Absorption spectroscopy on ${\mathrm{Ga}}_{0.47}$${\mathrm{In}}_{0.53}$As/${\mathrm{Al}}_{0.48\mathrm{L}}$${\mathrm{In}}_{0.52}$As multi-quantum-well heterostructures. I. Excitonic transitions

The physical properties of excitons (linewidth, binding energy, oscillator strength, reduced effective mass) in ${\mathrm{Ga}}_{0.47}$${\mathrm{In}}_{0.53}$As/${\mathrm{Al}}_{0.48}$${\mathrm{In}}_{0.52}$As multi-quantum-well heterostructures (MQWH’s) as a function of the well width and thus of the quasi-two-dimensional (2D) character of the respective MQWH were investigated by absorption and magnetoabsorption experiments. Samples lattice matched to InP with well widths ranging from 2.3 to 13.8 nm were grown by molecular-beam epitaxy. Double-crystal x-ray diffraction was used to determine the structural perfection and the individual layer thicknesses of the MQWH. The intrinsic statistical composition fluctuation of the ternary ${\mathrm{Ga}}_{0.47}$${\mathrm{In}}_{0.53}$As well material is found to be the dominant contribution to the linewidth of the excitonic transition. With decreasing well width the binding energy of the electron–heavy-hole exciton increases up to 9±2 meV for a well width of 3.4 nm. Similarly we observe a strong increase of the excitonic oscillator strength and of the reduced effective mass. A quasi-2D carrier system in this MQWH is realized for well widths of 3 to 5 nm.