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Y.C. J

High-performance 4H-SiC-based ultraviolet p - i - n photodetector Xiaping Chen, Huili Zhu, and Jiafa Cai Zhengyun Wua. Y.C. J. INTRODUCTION. Due to the wide band gap of SiC (4H-SiC ~3.25 eV cut-off wavelength ~380nm).

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Y.C. J

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  1. High-performance 4H-SiC-based ultraviolet p-i-n photodetectorXiaping Chen, Huili Zhu, and Jiafa CaiZhengyun Wua Y.C. J

  2. INTRODUCTION • Due to the wide band gap of SiC (4H-SiC ~3.25 eV cut-off wavelength ~380nm). • photodetectors utilizing this material should have the advantage of a good visible-blind/solar-blind performance. • very low dark current which can be many orders of magnitude lower than the dark current of conventional Si detectors.

  3. 0.38 Ω EXPERIMENT 70 nm 0.02 Ω Passivation此層用來防止漏電流 FIG. 1. Cross-sectional view (a) and top view (b) of 4H-SiC ultraviolet p-i-n photodetector.

  4. RESULTS AND DISCUSSION • A. Electrical characterization 1. Capacitance-voltage 0.7 FIG. 2. C-V characteristics i.e., 1/C2-V of the 4H-SiC p-i-n photodetector.

  5. RESULTS AND DISCUSSION • 藉由下列公式可計算出內建電壓Vbi，在所給的條件下計算出Vbi為~0.3V 藉由下列公式可計算出空乏區的寬度，在0V時W=0.6μm，而在0.7V時W=0.5um 在>0.7V對SiC之sample的i-layer空乏區寬度將變窄.

  6. RESULTS AND DISCUSSION 藉由下列公式可計算出1/C2用來描述1/C2對V的曲線電壓從0.7V到3.0V • 經由上列公式可已得到所算出的Vbi為3.0V，所量測到的為2.97±0.05V所以以符合所預估的值

  7. 在270nm的UV光照射下得到平均光電流可達6.0nA RESULTS AND DISCUSSION 2. Current-voltage 差了4個orders 12.5pA/mm2 12.5pA/mm2 FIG. 3. I-V characteristics dark current and photocurrent of the 4H-SiC p-i-n photodetector.

  8. RESULTS AND DISCUSSION 0.13 A/W • B. Photoresponse characterization 0.16 mA/W FIG. 4. The spectral responsivities of the 4H-SiC ultraviolet p-i-n photodetector under different reverse biases.

  9. RESULTS AND DISCUSSION • At wavelengths shorter than 240 nm, the quantum efficiency decreases as the wavelength decreases. • The spectrum shows a long wavelength cut off at 380 nm. At wavelengths longer than 380 nm, the 4H-SiC ultraviolet p-i-n detector shows the rarely low photoresponse. ※補充 SiC的Eg為3.25左右所以截止波長在380nm 1240/3.26=380nm

  10. RESULTS AND DISCUSSION 藉由下列公式可計算出外部量子效率 上述公式也可經由以下列公式來進行計算

  11. RESULTS AND DISCUSSION • 在270 nm時，經下列計算可以得到外部量子效率為 61 % 在380 nm時，經下列計算可以得到外部量子效率為 10-2 %

  12. CONCLUSIONS • Although 4H-SiC material is not intrinsically solar-blind, • the photodetector based on it appears to be a good potential candidate for solar-blind ultraviolet detection when employed with proper solar-blind interference filters. • solar-blind  290nm

  13. Reference • http://www.led-shop.com.tw/page38.htm LED原理 • http://www.ecn.purdue.edu/WBG/Introduction/Index.html為何使用SiC • 光電元件導論 2nd第11章 全威圖書有限公司 • 半導體元件物理及製作技術

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