Preparation of electron waveguide devices on GaAs/AlGaAs using negative-tone resist calixarene
We present a technique for the preparation of positively defined multiply connected electron waveguides on modulation-doped GaAs/AlGaAs heterostructures. This technique is based on a mix-and-match combination of electron-beam lithography (EBL) with standard photo lithography. Low-energy EBL on high-resolution negative-tone resist calixarene allows a nearly proximity-free positive definition of nanostructures with a minimum line width of about 25 nm. Subsequent to the EBL process the device leads and contacts are defined in photoresist with standard lithographic techniques. A single-step wet-chemical etch transfer enables the low-damage formation of isolated and multiply connected electron waveguides as well as large-area reservoirs. A 150 nm wide and 0.3 µm (1.2 µm) long quantum wire prepared by this technique shows quantized conductance with a maximum energy separation of 9.8 meV (10.9 meV) between the lowest one-dimensional subbands.