Study of bound exciton excited state structure using photothermal ionisation spectroscopy

Photothermal ionisation spectroscopy (PTIS) has been used for many years to study the electronic structure of dopants in semiconductors, but to our kn owledge it has been applied only once to the study of isoelectronic bound e xciton (BE) states. The absence of any substantial literature on the subjec t raises the question as to whether some fundamental factors preclude the o bservation of the sharp line transitions from the exciton excited states. W e have attempted to measure PTIS effects in a range of BE systems in silico n, but only certain systems prove amenable to the technique. In addition to data on the C-line (which has been reported in another study), PTIS spectr a of BE complexes at two other well-studied centres in silicon are reported , which are generally comparable to published photoluminescence excitation (PLE) and absorption spectra. The intensities of the lines do not show, in all cases, the expected systematic temperature dependence, demonstrating ex treme temperature sensitivity, with thermal activation energies different t o those obtained from photoluminescence (PL) temperature dependence data. F inally, we comment on the potential of the technique for the study of excit ed states of BE in silicon. (C) 1999 Elsevier Science B.V. All rights reser ved.