Time dependence of quantum well recombination luminescence in a bipolar AlAs/GaAs resonant tunnelling structure

The tunnelling transport of electrons and holes is investigated in a double-barrier AlAs/GaAs resonant tunnelling light-emitting diode (RTLED) biased below flat band ( approximately equals 1.5 V) using time-resolved photoluminescence (PL) spectroscopy. For photon energies above the confined exciton transition, a fast decaying PL component is observed which is ascribed to electron escape after e-h pair creation inside the well, with a characteristic time of 1 ns close to flat band and decreasing with electric field in the well. Below 1.1 V, photocarriers generated outside the well give rise to a slow decay component with characteristic times up to 3 ns, which is attributed to slow nonresonant tunnelling of electrons and holes from the respective depletion layers into the well. At lower external bias (higher field) the overall decay becomes faster due to faster hole tunnelling, as indicated by a qualitative change of the time dependence of the PL signal, and the relative growth of the light-hole exciton PL. © 1998 Elsevier Science B.V. All rights reserved.