A. Mask layout

All sets of masks used in this work were designed and fabricated at IGS-1 in Forschungszentrum Juelich. The optical lithography mask consists of a glass plate (commonly quartz, borosilicate glass or fused-silica) on which chromium patterns are defined by means of electron beam lithography. In this appendix, a brief overview of the mask layouts is presented focusing on the polyamide planar process (see section 5). Each step of the device preparation required an optical lithography mask:

1. mesa definition by reactive ion etching;
2. self aligned ohmic contacts deposition;
3. diode electrical isolation etching;
4. diode planarization / passivation;
5. bond-pads, low-pass filter and resonant circuit deposition.

Steps 1, 2 and 5 rely on a positive lithographic process, and steps 3 and 4 on a negative one.

In the case of the air-bridge process, two further layers are required. A detailed explanation of the optional air-bridge process is given in section 5.6.