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We show that silicon acceptors can be neutralized in p-type GaAs: Si. SIMS analysis shows that the deuterium concentration closely follows the net acceptor concentration. Infrared absorption spectroscopy reveals lines at 2094.7cm-1 and 1514.5cm-1 in hydrogenated and deuterated samples respectively. The ratio r of the two frequencies is 1.383 indicating that the lines are related to hydrogen isotopes. The reduction of the intensity of the local vibrational mode (LVM) of SiAs after neutralization is consistent with the formation of SiAs-H bonds. From SIMS data, it is concluded that most of the hydrogen present in the passivated material is complexed with silicon. A microscopic model of the Si-H complex is proposed.

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Infrared absorption spectroscopy has been performed on hydrogenated and deuterated n-type silicon-doped GaAs. It reveals the presence of a sharp vibrational mode at 890 cm−1 in hydrogenated samples and at 637 cm−1 in deuterated ones. These bands are absent in undoped GaAs. Analysis of the isotopic shift frequency reveals that the band is associated with a hydrogen–arsenic bond where arsenic is supposed to sit as a first nearest neighbor of the silicon donor atom giving rise to (SiAs3)As-H complexes. Isochronal annealing experiments show the direct correlation between the absorption line intensity and the amount of neutralized donors, confirming the view that the extra electrons of the silicon donors are involved in the hydrogen–arsenic bonds.