Lateral tunneling in point contacts

The Shubnikov–de Haas oscillations of the resistance of a point contact formed in the two-dimensional electron gas of ${\mathrm{Al}}_{\mathit{x}}$ ${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As/GaAs heterostructures via the lateral field effect are investigated for a series of values of the confining gate voltage ${\mathit{V}}_{\mathit{g}}$. Giant magnetoresistance oscillations are observed for values of ${\mathit{V}}_{\mathit{g}}$ close to the threshold voltage. An analysis of the differential channel resistance dV/dI as a function of the voltage drop V over the point contact shows that these oscillations are due to lateral tunneling through the point contact.