Effects of different processes with hydrogen on the photoluminescence of GaAlAs:Si grown by molecular beam epitaxy

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Abstract
We present a study on low‐temperature photoluminescence (PL) of Si‐doped Ga1−xAlxAs (n ∼ 1×1017 cm−3, 0.2≤x≤ 0.5) grown by molecular beam epitaxy (MBE) either in the presence and in the absence of a hydrogen backpressure and/or post‐growth hydrogenated by exposure to a hydrogen plasma; we show that GaAlAs grown with hydrogen has a PL efficiency higher than that of material grown without hydrogen by a factor of up to 20; even more interestingly, the relative enhancement of transitions related to excitons and to shallow donors and acceptors is so large that the two kinds of PL spectra are qualitatively different. On the contrary, independently on whether material grown without hydrogen is post‐growth hydrogenated, the spectral features of PL spectra are dominated by transitions involving relatively deep donors and/or acceptors. Our results suggest that the two treatments with hydrogen act on deep levels of different origin.