Tunneling through single AlGaAs barriers

Tunneling transfer through Alsub0.35Gasub0.65As barriers is studied in asymmetric double quantum well structures by time-resolved photoluminescence measurements in the pico- and femtosecond regime. A large variety of electron and hole resonances is detected when electric fields of both signs are externally applied. The ground state resonance shifts, when the electrons tunnel in the reserve direction, revealing the importance of excitonic effects. Longitudinal optical phonon assisted tunneling plays a minor role for narrow quantum wells in comparison to impurity or interface roughness assisted transfer. Resonant electron tunneling times depend exponentially on the integrated square root of the tunneling barrier height and are an order of magnitude faster than resonant hole tunneling times. The n=2 to n=1 electronic intersubband scattering time in a 10 nm quantum well is determined to be 550 fs measuring the transfer time through a thin barrier.