ELECTROLUMINESCENCE AND HIGH-FIELD DOMAINS IN GAAS/ALGAAS SUPERLATTICES

Photoluminescence, electroluminescence, and current measurements are used to probe the internal field in an n+-n-n+ GaAs/AlGaAs superlattice. At low bias voltages, the photoluminescence spectrum shows several peaks arising from electric field domains in the superlattice. Their positions correlate with features in the current-voltage characteristic and are consistent with a simple calculation of the Stark shift. Above the threshold voltage for impact ionization we observe spectrally narrow electroluminescence (width 3.5 meV). The energy of this emission coincides with the zero-field photoluminescence signal, indicating that electrons and holes screen the applied electric field in the quantum wells.