Photoluminescence of GaAs grown by metallorganic molecular beam epitaxy inspace ultra-vacuum

Low-temperature photoluminescence and selective pair luminescence has been used to identify shallow acceptor levels in undoped GaAs epilayers grown by molecular beam epitaxy and metallorganic molecular beam epitaxy (triethylg allium/As-4) in the ultra-vacuum of space generated in the wake of the free flying Wake Shield Facility satellite (Space Shuttle Colombia mission STS 80). The low-temperature photoluminescence spectra are typical of high-puri ty GaAs. The near-band-edge excitonic luminescence are found to be dominate d by donor bound excitons. Carbon C-As appears as the main residual accepto r impurity and excited state spectroscopy clearly identifies the presence o f zinc residual acceptor (Zn-Ga). Finally, the absence of a Be impurity, in troduced in large quantities to the growth environment prior to the MOMBE g rowth, suggest a minimized memory effect on the free flyer. (C) 2000 Elsevi er Science B.V. All rights reserved.