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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
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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
S
M
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 ultravioletvisible 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