Luminescence excitation spectroscopy on ${\mathrm{Ga}}_{0.47}$${\mathrm{In}}_{0.53}$As/ ${\mathrm{Al}}_{0.48}$${\mathrm{In}}_{0.52}$As quantum-well heterostructures

We have performed low-temperature (5–30 K) photoluminescence excitation spectroscopy on ${\mathrm{Ga}}_{0.47}$ ${\mathrm{In}}_{0.53}$As/${\mathrm{Al}}_{0.48}$ ${\mathrm{In}}_{0.52}$As quantum-well heterostructures lattice matched to InP which were grown by molecular-beam epitaxy. Excitation spectroscopy using a tunable KCl:Tl color-center laser allows us to measure the energy shift of the first electron to heavy-hole subband transition in absorption for quantum-well widths down to 10 nm. In samples with well widths of 25 and 35 nm, higher subband transitions are also identified in the excitation spectrum. Comparison of the experimental subband energy shifts with calculated data shows good agreement for well widths down to 10 nm, when a finite square-well potential with conduction- and valence-band discontinuities of 0.5 and 0.2 eV, respectively, is assumed. This band offset is consistent with data determined by the C-V profiling technique.