Analysis of photoassisted thermal recovery of metastableEL2 defects in GaAs

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Abstract
The thermal recovery characteristics of the photoquenched absorption of EL2 defects in GaAs are surveyed for a variety of samples, including undoped and Cr-doped semi-insulating samples and undoped and oxygen-doped n-type semiconducting samples, to demonstrate the material dependence of this process. Emphasis has been placed on analyzing a particularly strong photoassisted thermal recovery process observed in oxygen-doped, n-type semiconducting samples. This process has two unusual features: (i) it competes with the quenching process by virtue of its similar spectral range (1.0–1.4 eV), and (ii) it has a reduced thermal activation energy of ∼0.08 eV, yet the material displays the usual thermal recovery characteristic in the dark. The variety of thermal recovery processes existing in different samples implies the possibility that metastable defects can exist with structural modifications, possibly related to the impurity content of the host material.