NOVEL NONLINEAR TRANSPORT PHENOMENA IN A TRIANGULAR QUANTUM-WELL

We have measured transport properties in an AlGaAs/AlxGa1-xAs triangul ar quantum well whose energy spectrum has been varied by means of a ga te bias. We have observed several non-linear effects in the lateral co nductance arising at positive gate voltages as the increasing Fermi le vel is moved towards the lowering energy positions of the excited subb ands in the quantum well. We interpret our results in terms of electro n population of the excited subbands in which electrons possess low mo bility. Finally, we find new features at high lateral voltages which a re considered to be evidence of previously predicted electrophonon res onance.