Concentrations of neutral and ionized deep donor EL2 in undoped, semi-insulating GaAs crystals were obtained using the near-infrared photoabsorption method. By varying the carbon content in the crystal in a range of 1015-1016 cm-3, it was verified that only 30% of the total carbon acceptors take part in compensation of EL2, i.e., [EL2+]=0.3[C]. This contradicts with either the conventional two-level model which demands [EL2+]=[C] or the recent findings of electron paramagnetic resonance measurements indicating [EL2+]≫[C] . A model is presented to moderate these contradictions, which includes presence of indirectly carbon-related donor and electrically active and inactive two types of EL2. An evidence to support the model is given by a recent nuclear-magnetic resonance measurement by the same author [Appl. Phys. Lett. 57, 398 (1990)].
ASJC Scopus subject areas
- Physics and Astronomy(all)