RESONANT-TUNNELING BETWEEN PARALLEL, 2-DIMENSIONAL ELECTRON GASES - A NEW APPROACH TO DEVICE FABRICATION USING IN-SITU ION-BEAM LITHOGRAPHY AND MOLECULAR-BEAM EPITAXY GROWTH

Using the techniques Of in situ focused ion beam lithography and molecular beam epitaxy regrowth high quality, patterned back gate, double quantum well devices have been fabricated. Independent ohmic contacts were made to the two two-dimensional electron gases (2DEGs) using a ''selective depletion'' scheme, and using further gates the carrier densities in each well were controlled. Resonant tunneling between the two electron gases was observed as a function of carrier density in each 2DEG, and as a function of the bias applied between the two wells. Extremely large peak-to-valley ratios were observed, resulting from removal of unwanted parallel tunneling paths.