Low-temperature photoluminescence properties of high-quality GaAs layers grown by molecular-beam epitaxy

Low-temperature photoluminescence (PL) measurements have been performed on several molecular-beam epitaxial high-quality GaAs layers showing varied electrical characteristics (nominally undoped and intentionally doped n or p type). This work is carried out with a view to investigate the influence of the centers responsible for the defect–bound-exciton emissions (d,x) on the electrical properties of the layers. After a systematic study of the luminescence properties of the d,x emissions as a function of the electrical nature (doped n or p type), residual p doping level, PL excitation intensity, and sample temperature, we came to the following conclusion: In addition to the prominent residual carbon acceptors, at least a part of p conduction in nominally undoped p-type layers could come from the centers responsible for the d,x emission at 1.5109±0.0003 eV. This suggestion is tentatively ascertained by detecting an acceptor emission at ∼1.496±0.001 eV, shallower than the carbon acceptor about 3 meV. All these results in addition to those related to the detection of deeper acceptors in the spectral range 1.46–1.49 eV are presented and discussed.