MAGNETORESISTANCE OF A LATERAL CONTACT TO A 2-DIMENSIONAL ELECTRON-GAS

Lateral Nb contacts to a high-mobility two-dimensional electron gas (2 DEG) in InGaAs heterostructures are studied. Below T-c of Nb a pronoun ced non-linearity due to the superconducting energy gap is observed in the differential resistance. The Nb/2DEG interface reveals an enhance d zero-bias resistance. In normal state, a drastic decrease of the res istance with increasing magnetic field perpendicular to the plane of t he structure is observed. It is explained in terms of a confinement of electron trajectories near the interface with increasing magnetic fie ld yielding an enhanced number of transmitted carriers. The suggested model shows good agreement with experiment. We conclude that the magne tic field strongly influences the effective conductance of weakly tran sparent contacts.