  A fabrication method for electronic quantum Hall Fabry-Perot interferometers
(FPI) is presented. Our method uses a combination of e-beam lithography and
low-damage dry-etching to produce the FPIs and minimize the excitation of
charged traps or deposition of impurities near the device. Optimization of the
quantum point contacts (QPC) is achieved via systematically varying the etch
depth and monitoring the device resistance between segmented etching sessions.
The etching is stopped when a desired value of resistance is obtained. Finer
control of interference trajectories is obtained by the gate metallized inside
the etched area by e-beam evaporation. Our approach allows for a control of the
delicate potential bending near the quantum well by tuning the confining
potential of the quantum point contacts.
