Identification of EL2 in GaAs

Abstract

Combining electron paramagnetic resonance under optical excitation, deep level transient spectroscopy, electron irradiation, annealing, and quenching on LEC semi-insulating GaAs and lightly Si-doped material grown in the same way as the semi-insulating material, we have shown that (i) the irradiated material contains two types of defects related to the antisite AsGa, one As∇Ga, present before irradiation, identified to EL2 from its characteristic photoquenching behavior and the other As*Ga, created by the irradiation, stable under photoexcitation; (ii) As∇Ga anneals partially under a 850 °C thermal treatment followed by a quench and the remaining defects are transformed into As*Ga; (iii) further annealing around 120 °C converts As*Ga into As∇Ga, the process being thermally activated (0.5±0.2 eV). From these results and using observations of absorption on vibrational modes of the C-As interstitial pair in electron irradiated material, we are able to conclude that As*Ga is the isolated antisite and As∇Ga, i.e., EL2, is a complex of an As antisite and an As interstitial.

NewAsGarelated center in GaAs

“…Thus it is surprising that there is still controversy over the microscopic structure of EL2, i.e. , whether it is an isolated Aso, , center [2,3] or a complex with another defect, say, the arsenic interstitial As; [4]. Over the years there has been evidence usually from a single experiment of one type or another that there is more than one "EL2-like" defect.…”

Absolute Pressure Dependence of the Second Ionization Level of EL2 in GaAs

“…A value of av = -0.7 e V [ 16] for the hydrostatic deformation potential of the valence band, as determined using transition metal deep levels as references, corresponds to a pressure derivative of 9 meV GPa-1. Using this value, the absolute pressure derivative of EL2(++/+) becomes, (2).…”

Defect studies in low-temperature-grown GaAs

“…It was believed that the intricacy of a defect complex was required to achieve more than one configuration 180 yielding a local minimum in energy. Thus it was proposed that an ASGa plus an Asi at two interatomic distances from the ASGa formed the EL2 detect (Von Bardeleben, et al 1985, Von Bardeleben, et al 1986). This model is supported by the results of optically detected EPR and ENDOR measurements (Meyer, et al 1986).…”