Abstract

The occurrence of the excited triplet state in crystalline materials has long been associated with molecular and related crystals which have been investigated by a variety of techniques for ~20 years (e.g. see articles in Clarke (1)) whereas in semiconducting crystalline materials the excited or exciton state has generally been associated with electron-hole pairs where the orbital character of the holes (J = 3/2) is reflected in the electronic structure. However, in recent years a combination of detailed luminescence spectroscopy combined with optically detected magnetic resonance (ODMR) studies have demonstrated that in the case of defect complexes which place the host lattice into canpression, the orbital angular momentum of a bound hole is quenched; bound exciton formation is then between two S = 1/2 particles. The resulting singlet and triplet spectra observed in many materials, but particularly Gap, show that donor and acceptors aggregate to give a wide variety of isoelectronic or isovalent centres and recombination via these centres is the dominant radiative process. (2)

© 1984 Optical Society of America