Quantum-confined excitonic states at high-quality interfaces in GaAs(n type)/${\mathrm{Al}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As(p type) double heterostructures

We report 1.8-K H-band photoluminescence (PL) from abrupt, high-quality GaAs(n type)/${\mathrm{Al}}_{0.3}$${\mathrm{Ga}}_{0.7}$As(p type) double heterostructures prepared by metalorganic chemical vapor deposition, versus GaAs thickness (0.1–2.0 μm), 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 μs. 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.