ICDS Conference, Sendai, Japan, 7.95

INTERSTITIAL HYDROGEN AND THE DISSOCIATION OF C--H DEFECTS IN GAAS

S. J. Breuer, R. Jones,

Department of Physics, University of Exeter, Exeter, EX4 4QL, UK.

S. Öberg

Department of Mathematics, University of Luleå, Luleå, S95187, Sweden.

P. R. Briddon

Department of Physics, University of Newcastle, Newcastle, NE1 7RU

Abstract

Local--density--functional calculations using a real--space cluster approach are used to model interstitial hydrogen in GaAs and the dissociation of the C--H and C--H$^-$ complexes. The equilibrium site is found to be on a Ga--As bond axis for H$^0$ and H$^+$ an d at a Ga anti--bonding site for H$^-$. It is also shown that a H$_2$ molecule is stable in interstitial space and has a lower energy than the two possible H$_2^*$ defects and than widely separated single interstitial hydrogen atoms. The study of hydrogen in pure GaAs also yields the result that interstitial hydr ogen is a negative--U defect. It is found that the energy barrier to the dissociation of the C--H complex is 1.8 eV, but that this is reduced to 0.9 eV for C--H$^-$. Comparison is made with recent experimental results and implications for current containing devices are discussed.

Keywords: C-H, dissocation, interstitial hydrogen, GaAs, ab initio