Enhancement in photoluminescence from 1?eV GaInNAs epilayers subject to 7 MeV electron irradiation
We have investigated the influence of 7 MeV electron irradiation (1014?1015?cm?2?range) and subsequent rapid thermal annealing (RTA) on luminescence efficiency of nearly lattice-matched 1?eV GaInNAs-on-GaAs epilayers, grown by molecular beam epitaxy. The study has been done by means of 9?K photoluminescence (PL) and 300?K photoreflectance (PR) spectroscopy. Electron irradiation was found to directly promote a notable increase in PL intensity. A further PL enhancement, remarkable at the higher annealing temperature, has been seen upon two RTA stages (at 800 and 900??C) applied to irradiated samples as compared to a non-irradiated sample. This irradiation-promoted PL enhancement upon annealing occurred with a small additional blue-shift of PL for the lower temperature-annealed samples but no additional shift in PL was noted for the higher temperature-annealed sample. The additional annealing-induced PL blue-shift was mainly due to an irradiation-promoted enhancement in In?N bonds formation, whose magnitude does not appear to depend on dose within the studied range.