ETCHED-BACKGATE FIELD-EFFECT TRANSISTOR STRUCTURE FOR MAGNETOTUNNELING STUDY OF LOW-DIMENSIONAL ELECTRON-SYSTEMS

We fabricated field effect transistors having independent ohmic contac ts to individual two-dimensional-electron gases in a double quantum we ll structure by etching the backgate (BG) area to 30 mu m-thick, while keeping the major part of the substrate thick for ease of handling (6 0 mu m). By this approach, it was made possible to form independent oh mic contacts with applied voltage to BG of about -60 V. We investigate d the device by measuring the tunneling conductance as a function of t emperature, in-plane magnetic field and carrier density. The temperatu re dependence showed that the broadening of resonant tunneling peak or iginated from the ionized impurity scattering and the electron-electro n scattering. The in-plane magnetotunneling has shown two peaks at par ticular fields expected from the carrier densities in each well. These results indicate that the uniformity of the thick ness of the etched BG area is good enough to allow the study of 2D-2D tunneling spectrosc opy. (C) 1998 Elsevier Science Ltd. All rights reserved.