Electro-Optical Performance Study of 4H-SiC/Pd Schottky UV Photodetector Array for Space Applications

Abstract

4H-SiC Schottky photodetector array was fabricated by pulsed dc sputter deposition of palladium thin film as UV semitransparent Schottky contact on active pixel. Results of electro-optical characterization of these devices as a function of temperature varying from 33 to 393 K are presented. A peak spectral responsivity of 122 mAW−1 at 280 nm is observed. Further, spatial response uniformity for a 4 mm $\times4$ mm detector, scanned by UV spot of $100~\mu \text{m}$ diameter, is within ±5%, whereas the crosstalk between the pixels in $4\times 2$ detector array with a pixel size of $850\,\,\mu \text{m}\,\,\times 850\,\,\mu \text{m}$ is within 1.3%. Capacitance at near zero bias is around 11 pF and 4.79 pF at a reverse bias of 30 V. From the ${I}$ – ${V}$ characteristics, the calculated Schottky barrier height is 1.37 eV for 70 A thick palladium metal film on 4H-SiC as against the theoretical value of 1.96 eV. Operating temperature studies on detector UV response at 300 nm have shown that the photo-current response at 113 K falls to half of its peak value at ambient. The responsivity of the detectors at 248-nm wavelength is almost constant over a wide temperature range of 33 to 393 K.