Dynamics of H trapped by defects in type IV and III–V semiconductors

Recent progress and new results are discussed from anelastic spectroscopy studies of H complexes with substitutional dopants and vacancies in Si, GaAs and InP. Anelastic relaxation processes due to the reorientation of H around dopants are found in the case of acceptors (B in Si and Zn in GaAs) but not of donors (P in Si, and Si Ga in GaAs). It is argued that this is an indication of bond-center occupancy in the first case and anti-bonding in the second one, in accordance with theoretical predictions. The reorientation rate of H around B in Si can be followed over 11 orders of magnitude, including the data from infra-red spectroscopy, and a deviation from an Arrhenius law with effective barrier of 0.22 eV at low temperature indicates the involvement of tunneling in the reorientation process. The relaxation rate of H and D in GaAs:Zn is much faster than any other dopant-H complex studied so far, and the analysis of the process demonstrates a totally non-classical nature of the H motion. This also provides evidence of off-centre occupation of H from the Zn–As bond. In InP, a new relaxation process has been found, which is present only in the semi-insulating state. It is argued that the defect is an In vacancy with the P dangling bonds partially saturated by H, and that such vacancy-H complexes have a role in obtaining semi-insulating InP, which is of technological interest.