J. Phys. I France
Volume 1, Numéro 10, October 1991
Page(s) 1511 - 1527
DOI: 10.1051/jp1:1991223
J. Phys. I France 1 (1991) 1511-1527

The EL2 center in GaAs: symmetry and metastability

N. 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 $_{\rm {3V}}$ as the type of symmetry for this antisite double donor whose charge states - D + = As Ga, D 0= (As $_{\rm i}$V $_{\rm Ga}$) 0 and D ++ = (As $_{\rm i}$V $_{\rm Ga}$) ++ - 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 $\Gamma$, 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 + + $hv \rightarrow$ 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 + $h \rightarrow$ D + reaction.

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