Donor–acceptor-pair spectroscopy of GaAs grown in space ultravacuum
1999; American Institute of Physics; Volume: 74; Issue: 22 Linguagem: Inglês
10.1063/1.123338
ISSN1520-8842
AutoresG. Neu, M. Teisseire, A. Freundlich, Charles Horton, A. Ignatiev,
Tópico(s)Quantum Dots Synthesis And Properties
ResumoSelective pair luminescence has been used to identify shallow acceptor levels in undoped GaAs epilayers grown by molecular beam epitaxy (MBE) in the ultrahigh vacuum of space generated in the wake of the free-flying Wake Shield Facility satellite (Space Shuttle Endeavor mission STS69). The low-temperature photoluminescence spectra are typical of high-purity GaAs. Unlike for conventional MBE-grown undoped GaAs where the near-band-edge excitonic luminescence is dominated by acceptor-bound excitons, the space-grown GaAs near-band-edge luminescence was found to be dominated by donor-bound excitons. The comparison of measured ground (1S3/2) and excited acceptor states to published acceptor spectra leads to the identification of CAs as the main residual acceptor impurity in the layer. Furthermore, the existence of a donor–acceptor-pair emission band demonstrates that a second acceptor is electronically active. Excited-state spectroscopy clearly identifies the second residual acceptor as ZnGa, which is scarcely observed for GaAs samples grown in terrestrial MBE systems. In addition, the absence of a Be impurity, introduced in large quantities to the growth environment prior to the epilayer growth, suggests a minimized memory effect on the free flyer as opposed to terrestrial chambers.
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