INDEPENDENT CONTACTING TO ELECTRON LAYERS IN A DOUBLE-QUANTUM-WELL SYSTEM USING PD-GE SHALLOW OHMIC CONTACTS

A novel recess technique is used to produce reliable Pd-Ge ohmic conta cts to GaAs/AlGaAs high mobility two-dimensional electron gas (2DEG) s ystems, operating down to cryogenic temperatures. By altering the dept h of the recess the diffusion length of the contacts is found to be le ss than 20 nm. Pd-Ge shallow ohmic contacts were also used for forming independent contacts to two 2DEGs in a double quantum well structure where the 2DEGs are separated by only a 20 nm AlxGa1-xAs(x=0.3) barrie r. Tunnel current measurements and magnetoresistance analysis confirme d that the layers could be probed individually and that the carrier de nsities and mobilities of the separate layers could be accurately dete rmined.