Excitonic photoluminescence in high-purity InAs MBE epilayers on GaAs substrates

Temperature- and excitation-dependent photoluminescence measurements have been carried out on 0.7-5 mu m thick heteroepitaxial InAs layers grown by molecular beam epitaxy (MBE). Excitonic photoluminescence with linewidths down to 5 meV reveals the high optical quality of the epilayers despite the 7% mismatch between the InAs and the GaAs substrates. Peaks at 403 and 391 meV, which quench rapidly with increasing temperature, are attributed to bound excitons, and a sharp (7 meV FWHM) intense line at 417 meV is tentatively attributed to free excitonic recombination. A broad 18 meV wide band (peaking at 378 meV) which blue shifts with increasing excitation, characteristic of a donor-acceptor pair transition band, is reported for the first time in InAs.