On photoluminescence and photoreflectance of 1-eV GaInNAs-on-GaAs epilayers

The effects of growth temperature (410 and 470 °C) and subsequent rapid thermal annealing (RTA) on luminescence performance of lattice-matched 1-eV GaInNAs-on-GaAs epilayers, grown by molecular beam epitaxy under constant fluxes, has been studied experimentally by 9-K photoluminescence (PL) and 300-K photoreflectance (PR) spectroscopy. The near band edge PL has been found to noticeably decrease and red-shift as the growth temperature (Tgr) is reduced from 470 to 410 °C. This red-shift is the consequence of a reduction in the alloy band gap with decreasing Tgr, as confirmed by PR. An N-related broad PL band, whose intensity remarkably enhances with increasing Tgr, has been detected at longer wavelengths in the 9-K PL's. Post-growth RTA (1 min at 800 °C) significantly enhanced the near band edge PL but it did so at the expense of a PL blue-shift: the more the PL enhancement and blue-shift the lower the Tgr. This annealing-induced blue-shift is due to In-N bonds formation, whose magnitude enhanced as the Tgr is decreased. The broad PL band also enhanced upon the RTA, but the ratio between its intensity and the intensity of the near band edge PL reduced, especially for the sample grown at 410 °C. 7-MeV electron irradiation to the dose of around 1015 cm−2 applied prior to annealing considerably reduced the broad PL band upon annealing.