TIME-RESOLVED PHOTOLUMINESCENCE INVESTIGATIONS OF ELECTRIC-FIELD DOMAIN FORMATION IN GAAS-ALAS SUPERLATTICES

The electric-field domain-formation time of an undoped GaAs-AlAs super lattice embedded in a p(+)-i-n(+) diode is investigated by time-resolv ed photoluminescence (PL). After optical excitation of electron-hole p airs with an ultrashort light pulse, the previously homogeneous electr ic field breaks up into domains that can be observed by a splitting of the PL line due to the quantum-confined Stark effect. The PL dynamics is studied as a function of excitation density and applied voltage. A domain-formation time on the order of a few nanoseconds is found. Thi s time is unexpectedly short compared to the vertical transport time o f electrons through the entire superlattice.