Observation of precursor pair formation of recombining charge carriers

An experiment is presented which allows the observation of charge-carrier pair formation that precedes electronic transitions such as spin-dependent recombination or spin-dependent transport. It is based on an electrically detected magnetic-resonance-induced rotary echo sequence. The experimental demonstration is performed on precursor (spin) pairs of electrons in the emitter layer of crystalline silicon/amorphous silicon heterostructures. Precursor pair-generation-rate coefficients extracted from these measurements are studied as a function of light intensity and are found to show only a minor dependence on the illumination level indicating that the pair generation is not determined by charge-carrier densities.