Enhanced exciton binding energy in InAs monolayers grown on (311)A GaAs substrates

We studied magneto-optical properties of ultra-thin InAsGaAs heterostructures deposited on GaAs (311)A surfaces. Sharp heavy- and light-hole exciton resonances, as well as the features due to exciton excited states are observed in photoluminescence (PL) and photoluminescence excitation (PLE) spectra. No Stokes shift between heavy-hole exciton peaks in PL and PLE spectra is found. From magneto-PLE spectra, exciton binding energy is measured to be 12 ± 1 meV, i.e. three times higher than the surrounding GaAs matrix and ten times higher than the bulk InAs. We suggest the model of lateral confinement in monolayer InAs which enhances the exciton binding energy and suppresses the in-plane exciton transport.