Interband transitions in ${\mathrm{In}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As/${\mathrm{In}}_{0.52}$${\mathrm{Al}}_{0.48}$As single quantum wells studied by room-temperature modulation spectroscopy

Room-temperature phototransmittance and electrotransmittance of single quantum wells of ${\mathrm{In}}_{\mathit{x}}$ ${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As with ${\mathrm{In}}_{0.52}$ ${\mathrm{Al}}_{0.48}$As barriers have been used to study the excitonic interband transitions between the confined conduction- and valence-band states. Peak assignment has been confirmed by photocurrent spectroscopy. The lattice-matched (x=0.53) and strained (x=0.6) structures were considered for two different well widths of 50 and 250 Å. Transition energies and broadening parameters were measured from the spectra of the wide well samples and studied as a function of the principal quantum number. Reasonably good agreement between theory and experiment has been achieved by using published values of the electronic band-structure parameters. An observed monotonic increase of the linewidth with the quantum number has been associated with the presence of well-width fluctuations due to rough interfaces.