Farinfrared Magneto-Optics of the Shallow-Deep Impurity Transitions Using Diamond Anvil Cells

High pressure studies of electronic states of impurity donors in GaAs are reported. The diamond anvil high-pressure cell technique is applied to far-infrared magneto-optical experiments. Absorption due to the ls-2p(+) transition for different shallow donor species is investigated in transmission experiments using far-infrared laser radiation at pressures up to 40 kbar. A shallow-deep transition is observed for sulphur, silicon and tin donors close to 30 kbar, resulting in bleaching of the FIR absorption. The transition is similar to that for the Ge donor at 9 kbar observed previously with Unipress cells. Deep states responsible for quenching of FIR absorption are further investigated in photoluminescence experiments. They do not follow either the Γ or X conduction band. All these deep states which are resonant with the conduction band at ambient pressure have the attributes predicted theoretically of highly localized, weakly relaxed states with A 1 symmetry associated with substitutional impurities.