Hydrogen passivation of beryllium in p-type GaAs - art. no. 195204

The. structure, vibration frequencies, reorientation kinetics, and passivat ion mechanism of the complexes that include hydrogen and Be shallow accepto rs in crystalline GaAs have been investigated by an ab initio molecular dyn amics method. The stable configuration is found for the H atom located near a bond-centered site between the Be acceptor and a nearest neighbor As ato m. However, the hydrogen atom tends to move off the trigonal axis by 0.147 Angstrom. The bonding shows that the hydrogen saturates the As atom to leav e the Be acceptor threefold coordinated. The vibrations of Be and H are sep arate. The stretching frequency of hydrogen is similar to an arsine molecul e. The present calculations well reproduce the experimental value of reorie ntation energy for H motion between adjacent bond-centered sites about the Be acceptor in the stable configuration. A good agreement with experiment i s also found for the dissociation energy to account for the beryllium passi vation by hydrogen. It is H+ diffusing in and out the stable bond-centered site rather than H-0 in p-type GaAs. In tracking the hydrogen, the passivat ion mechanism of involving a H+ diffusion cation to neutralize the Be-Ga(-) acceptor can be resolved.