Optical investigation of tunneling in AlAs/GaAs/AlAs double-barrier diodes.

We describe time-integrated and time-resolved photoluminescence measurements made on a series of n-type symmetric and asymmetric AlAs/GaAs/AlAs double-barrier tunneling diodes. Optical measurements of the electron charge buildup in the well near the peak in the tunneling current are used to deduce the average dwell time. This is found to be shorter than expected for tunneling through a Γ-point AlAs collector barrier for barriers thicker than about 3 nm but can be explained if there is strong scattering into X-point valleys. Under high-intensity illumination rue also observe a substantial photoexcited hole current with clear tunneling peaks together with accumulation near the collector barrier and in the well