Photoluminescence study of the annealing behavior of transmuted impurities in neutron-transmutation-doped semi-insulating GaAs

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Abstract
In neutron-transmutation-doped GaAs irradiated with various fast neutron fluences, the annealing behavior of band-germanium acceptor [Ge(B-A)] transitions has been evaluated using the photoluminescence technique. In the fast neutron irradiation of ≤7.0×1017 cm−2, a few percent of transmuted Ge atoms behave as acceptors in As sites and more than 98% of the transmuted Ge atoms activate as donors in Ga sites. In the fast neutron irradiation of 3.7×1018 cm−2, the shift of Ge(B-A) transitions towards lower energies originates from the band-edge distortion. Removing the band-edge distortion by annealing above 790 °C leads to the increase in the Ge acceptor, accompanied by an increase of the peak intensity of Ge(B-A) transitions. The lower electrical activation of transmuted impurities (∼75%) arises from the high-temperature annealing required to remove the radiation damage. On annealing out the radiation damage, the peak shift of Ge(B-A) transitions based on the increase in the free carrier is discussed using the Burstein–Moss model.