Effects of uniaxial stress on the absorption lines of and the nature of the Jahn-Teller coupling

Abstract

Experiments showing the effects of uniaxial stress on the structure of the zero-phonon line (ZPL) obtained in the optical absorption spectrum from a ion in GaP are described and interpreted using a new theoretical model. It is found that the components of the ZPL are split when the stress is applied along the , and axes. These results together with the spectra observed without applied stress, show that previous energy level diagrams for this centre cannot be correct. A vibronic model is used to describe this system which includes coupling to e modes in the ground states, to both e and modes in the excited excited states and to modes between and . The model is shown also to give a good explanation of the published Zeeman data obtained from photoluminescence measurements as well as the new uniaxial stress data presented here. A brief discussion is given of the type of Jahn-Teller effect operational in this system emphasizing that it is not necessarily of the orthorhombic type in the excited state.

Dynamic Jahn-Teller effect in crystals doped with 3d ions

“…Titanium-doped -semiconductors have been the object of quite a large number of studies [16][17][18][19][20][21][22][23][24]. The interest in these compounds cames from the need of high resistivity materials with a good thermal stability for electronic and optoelectronic devices.…”

“…The electron paramagnetic resonance (EPR) spectra in GaP [20] and GaAs [17], the optical spectra of GaAs, [16,21] InP [21] and GaP [19,23,24] show evidence of JT effect. Conflicting interpretative models have been proposed in literature, and the more recent one, suggested by Al-Shaikh et al [24], considers a JT coupling to trigonal and tetragonal modes (even if in a not complete quantum mechanical treatment) which by analyses tells the effect of uniaxial stress on the optical spectra. The optical and paramagnetic properties of Ti 3+ -doped ZnS allow a detailed analysis of its level structure and the experimental results can be interpreted including a JT coupling in addition to CF and SO interaction [25].…”