Deep-ultraviolet (DUV) solar-blind photodetectors based on high-quality cubic boron nitride (cBN) films with a MSM configuration were fabricated with “l’Institut d’Electronique et de Microélectronique et de Nanotechnologie” (IEMN, France) and with Prof W. Zhang from City University of Hong Kong.
The design of interdigitated circular electrodes enables high homogeneity of electric field between pads. The metal fingers have been processed to 2 µm in width with 5µm spacing between the contacts (instead of 15 µm for previous LYRA design). We achieved good homogeneity and reproducible lithography patterns.
The DUV photodetectors present a peak responsivity at 180 nm with a very sharp cutoff wavelength at 193 nm and a visible rejection ratio (180 versus 250 nm) of more than four orders of magnitude. The characteristics of the photodetectors present extremely low dark current, high breakdown voltage, and high responsivity, suggesting that cBN films are very promising for DUV sensing.