Quantum-confined excitonic states at high-quality interfaces in GaAs(n type)/AlxGa1-xAs(p type) double heterostructures

We report 1.8-K H-band photoluminescence (PL) from abrupt, high-quality GaAs(n type)/Al0.3Ga0.7As(p type) double heterostructures prepared by metalorganic chemical vapor deposition, versus GaAs thickness (0.12.0 1/4m), to study dynamics of carriers quantum confined near heterointerfaces. Our time decays yield bimolecular kinetics, spectral peak shifts in time, and lifetimes (across the H-band PL) varying from nanoseconds to >50 1/4s. Numerical modeling yields a two-dimensional-exciton description with quantitative predictions for exciton binding energies, transition energies, charge densities, oscillator strengths, and lifetimes which, upon radiative decay, give rise to the observed H-band dynamics. We thus explain the observed kinetics and prove that H-band PL arises not from impurities, but from intrinsic bound excitons involving both heterointerfaces. Further, we find that such highly polarizable, spatially indirect, electron-hole systems may only be adequately understood in wide (non-quantum-well) structures. © 1991 The American Physical Society.