Optical studies of resonant and non-resonant tunnelling in GaAs/ AlxGa1-xAs quantum wells

We have used CW photoluminescence and photocurrent spectroscopy to study the vertical transport mechanisms in GaAs/AlxGa1-x As multiple quantum well p-i-n structures. In an x = 0.33 asymmetric coupled well sample we have observed resonant electron tunnelling through barriers as thick as 153 A above the transition field for spatially indirect recombination. In a superlattice with x = 0.4 we have observed both electron and hole resonant tunnelling. The temperature and intensity dependence of the photocurrent suggest that non-resonant tunnelling is assisted by charged impurity scattering below 100 K.