In order to elucidate the deep penetration mechanism of irradiation defects, the 2-dimensional electron gas which formed at the Ga0.7Al0.3As/GaAs interface (60 to 120nm from the surface) was irradiated with 1.4 to 10keV Ar ions and the resultant change in mobility was analyzed by making  in situ  Hall measurements at 90K. Annealing data indicated that the thermal diffusion of 2 types of defect took place at about 200 and 400K and caused a degradation of the mobility. Irradiation with 2keV electrons, after Ar ion bombardment, was also found to cause significant defect migration. It was concluded that the deep penetration was due to a long-range migration of both Ga and As interstitials that was caused by thermal diffusion and a recombination enhanced mechanism.

T.Kanayama, T.Wada, Y.Sugiyama: Materials Science Forum, 1995, 196-201 1939-42