J. Phys. I France 1 (1991) 1511-1527
The EL2 center in GaAs: symmetry and metastabilityN. T. Bagraev
A. F. Ioffe Physico-Technical Institute, Academy of Sciences of the USSR, Leningrad 194021, U.S.S.R.
(Received 22 May 1991, accepted I2 June 1991)
Photo-EPR, piezospectroscopic and Stark-effect photocapacitance data were used to determine the symmetry of the EL2 center in GaAs and to identify the mechanism that underlies its metastable behavior. The results unambiguously point to C as the type of symmetry for this antisite double donor whose charge states - D + = As Ga, D 0= (As V ) 0 and D ++ = (As V ) ++ - occupying, respectively, the positions on the site and in the tetrahedral and hexagonal interstices, are brought about, in the same order, by the wavefunctions of the , L and X valleys of the conduction band. The transition made by the EL2 center to a metastable state is the result of a charge exchange of the type 2D + + D 0 + D ++ , which causes the antisite As, defect to tunnel from its position at the site to a position in the tetrahedral interstice. Annealing of the center in this state proceeds at such temperatures and rates as are determined by the height of the energy barrier to the D 0 + D + reaction.
© Les Editions de Physique 1991