Evidence for the role of the indirect-gap electron states in tunnelling through thin AlAs barriers

An asymmetric GaAs/AlAs superlattice located at the interface of a p-n junction is shown to give rise to novel features in the current-voltage characteristics. The observation of negative differential resistance up to 300 K is reported. The data are found to be consistent only with tunnelling via the lowest (indirect) band gap through the AlAs barriers.