TRANSIENT CHARACTERISTICS OF ISOELECTRONIC BOUND EXCITONS AT HOLE-ATTRACTIVE DEFECTS IN SILICON - THE C(0.79 EV), P(0.767 EV), AND H(0.926 EV) LINES

The decay kinetics of isoelectronic bound excitons at hole-attractive defects in silicon is studied by means of time-resolved photoluminescence. From these measurements it is found that their radiative decay generally follows a multiexponential relationship due to fully unthermalized excited singlet (S=0) and triplet (S=1) states. In the case of the C(0.79 eV) line the intrinsic transient is described by two exponentials whereas in cases of the P(0.767 eV) and H(0.926 eV) lines a triexponential decay is found. From the temperature dependence of the time constants and amplitudes the energetic splittings of the singlet and triplet levels, the relevant singlet-to-triplet transfer times, as well as the radiative decay times of the singlet levels are determined. In all cases consistent results are found only if nearly equal initial excitation densities for the singlet state and for each of the three triplet substates are assumed. In the case of the P line thermalization of the triplet substates around 14 K is observed. In the case of the C line the intrinsic transition is superimposed by nonradiative, sample-dependent, excitation losses which are explained in terms of excited electron tunneling to surrounding defects which also obscures the third exponential.