Conductance oscillations induced by longitudinal resonant states in heteroepitaxially defined Ga0.25In0.75As/InP electron waveguides

We have measured at low temperatures the conductance of electron waveguides fabricated from modulation-doped quantum wells by wet etching and regrowth . We have found that, for a waveguide with abruptly changed geometry at the entrance and exit, the conductance shows oscillations, which are superimpo sed on a conventional conductance plateau structure. The periods and amplit udes of conductance oscillations depend on the length to width aspect ratio of the waveguide. In addition, the amplitudes of conductance oscillations decrease with increasing temperature. We propose that the observed oscillat ions are caused by the formation of longitudinal resonant electron states i n the waveguide, in analogy with optical Fabry-Perot effects. (C) 2000 Amer ican Institute of Physics. [S0003-6951(00)03616-0].