Electron Tunneling Time Measured by Photoluminescence Excitation Correlation Spectroscopy

Abstract

The tunneling time for electrons to escape from the lowest quasi-bound state in the quantum wells of GaAs/AlAs/GaAs/AlAs/GaAs double-barrier heterostructures with barriers between 16 Å and 62 Å has been measured at 80 K using photoluminescence excitation correlation spectroscopy. The decay time for samples with barrier thicknesses from 16 Å (≈ 12 ps) to 34 Å (≈ 800 ps) depends exponentially on barrier thickness, in good agreement with calculations of electron tunneling time derived from the energy width of the resonance. Electron and heavy-hole carrier densities are observed to decay at the same rate, in contrast to resonance-width calculations that indicate that heavy-hole tunneling times should be much longer than those for electrons. Reasons for this observation are discussed. Similar measurements in biased structures showing negative differential resistance are described.