Determination of barrier heights in heterostructures utilising real-space transfer of hot electrons

Preliminary work is reported on electrical transport in a GaAs/AlGaAs heterojunction test structure, aimed primarily at investigating the barrier height at the interface. The structure consisted of an n-GaAs layer in the form of a Hall bar, with an n-AlGaAs mesa standing proud on the upper broad face of the layer. Hot electrons were generated in the n-GaAs by applying a voltage pulse to the Hall bar current contacts, and the transfer of electrons across the junction interface led to the appearance of an open circuit voltage pulse across the junction. Experimental results obtained for a GaAs/Al0.43Ga0.57As structure were analysed using a simple theoretical model to give the value θ = (0.37 ± 0.06) eV for the barrier height at the interface. This preliminary result is shown to be satisfactory, and it is suggested that the experimental procedure described could provide a useful means of measuring small barrier heights at heterojunction interfaces.