High responsivity 4H-SiC Schottky UV photodiodes based on the pinch-off surface effect Antonella Sciuto, Fabrizio Roccaforte, Salvatore Di Franco, and Vito Raineri

Outline INTRODUCTION EXPERIMENTAL SETUP RESULTS AND DISCUSSION CONCLUSION REFERENCES

INTRODUCTION Some works in the last decade reported p-i-n UV detectors on SiC with promising UV performances and ultraviolet-visible rejection ratio of about 1002. Schottky diodes are majority carrier devices, thus allowing a faster response than p-n junctions.

EXPERIMENTAL SETUP M M M S S M 水平式 垂直式

示意圖 水平式的電極圖形 垂直式的電極圖形

Optical microscopy image of one of the fabricated devices, showing the interdigit front electrode with 11.4 m spaced metal stripes.

RESULTS AND DISCUSSION Photocurrent of vertical 4H-SiC interdigit Schottky photodiode with 5.4 m spaced metal stripes as a function of the reverse bias, under dark conditions and under illumination at 256 nm.

Internal responsivity vs wavelength of the vertical 4H-SiC Schottky UV detectors at a 20 V reverse bias. Close to the experimental data points,the calculated internal QE is also reported. In the investigated wavelength range, the maximum in the R, 160 mA/W, and in the internal QE, 78%, is reached at 256 nm.

Comparison of the photocurrent of vertical 4H-SiC Schottky UV detectors and planar MSM detectors with 11.4 m spaced metal stripes,under dark conditions and under illumination at 256 nm. The response of the vertical detector is a factor of 1.4 higher than that of the planar MSM structure.

CONCLUSION high responsivity 4H-SiC vertical photodiodes were demonstrated exploiting the surface pinch-off effect. The vertical photodiodes showed an ultraviolet-visible rejection ratio >7×103 and a responsivity a factor of about 1.8 higher than a conventional planar metal-semiconductor-metal structure.

REFERENCES High responsivity 4H-SiC Schottky UV photodiodes based on the pinch-off surface effect Comprehensive characterization of metal–semiconductor–metal ultraviolet photodetectors fabricated on single-crystal GaN Richardson’s constant in inhomogeneous silicon carbide Schottky contacts