Hole Tunneling Times Research Articles

Electron and hole tunneling times in GaAs/AlGaAs asymmetric double quantum well heterostructures

We present CW and time-resolved photoluminescence measurements on GaAs/AlGaAs asymmetric double quantum well heterostructures. Several samples (eight) have been considered in order to study the influence, on the carrier tunneling process, of both barrier thickness and energy separation between the levels in the different wells. A comparison between photoluminescence decay time of excitonic recombinations in the narrow well and wide well, under resonant and non resonant excitation, allows us to determine both the electron and hole tunneling times. Evidence of non resonant and LO phonon-assisted electron tunneling, resonant and near-resonant hole tunneling is found and discussed.

Time-Resolved Optical Investigation of Tunneling of Carriers Through Single AlxGa1-xAs Barriers

An asymmetric double quantum well structure consisting of a wide and a narrow quantum well separated by AlxGa1-xAs barriers of various thicknesses is used to investigate resonant and nonresonant tunneling of electrons as well as holes through a single barrier. The carrier transfer times are obtained by tracing the luminescence decay of the two quantum wells with picosecond time resolution as a function of an applied electric field. For the first time, resonant and nonresonant electron and hole tunneling times in one single structure are reported. Our results are compared with those of other groups. Idealized theoretical models cannot explain the experimental values.

Effect of collisions and relaxation on coherent resonant tunneling: Hole tunneling in GaAs/AlxGa1-xAs double-quantum-well structures.

Direct measurements of resonant and nonresonant hole tunneling times in a GaAs/${\mathrm{Al}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$As double-quantum-well structure show that tunneling time at resonance is considerably longer than expected for coherent tunneling or intersubband relaxation. We demonstrate that coherent tunneling and relaxation cannot be treated independently since the coherence is destroyed by collisions and relaxation. This leads to a large increase in the tunneling times observed at resonance. We show furthermore that resonant tunneling due to mixing between heavy- and light-hole states is less important than tunneling between heavy-hole states.

Hole tunneling times in GaAs/AlAs double-barrier structures

We have calculated hole tunneling times in GaAs/AlAs double-barrier structures taking quantum well band-mixing effects into account. Our results indicate that for sufficiently high hole temperatures and concentrations, band-mixing effects reduce average hole tunneling times from the pure heavy hole value to values comparable to electron tunneling times in the same structure. For very low hole temperatures and concentrations, band mixing is less important and average hole tunneling times should approach the pure heavy hole value. These results provide an explanation for previously reported experimental results in which electrons and holes were found to be characterized by very similar tunneling times.