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Kang et al. Nanoscale Research Letters 2011, 6:236

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Kang et al. Nanoscale Research Letters 2011, 6:236 http://www.nanoscalereslett.com/content/6/1/236 NANO EXPRESS Open Access Anti-reflective nano- and micro-structures on 4H-SiC for photodiodes Min-Seok Kang1, Sung-Jae Joo2, Wook Bahng2, Ji-Hoon Lee1, Nam-Kyun Kim2, Sang-Mo Koo1* Abstract In this study, nano-scale honeycomb-shaped structures with anti-reflection properties were successfully formed on SiC. The surface of 4H-SiC wafer after a conventional photolithography process was etched by inductively coupled plasma. We demonstrate that the reflection characteristic of the fabricated photodiodes has significantly reduced by 55% compared with the reference devices. As a result, the optical response Iillumination/Idark of the 4H-SiC photodiodes were enhanced up to 178%, which can be ascribed primarily. | Kang et al. Nanoscale Research Letters 2011 6 236 http www.nanoscalereslett.eom content 6 1 236 o Nanoscale Research Letters a SpringerOpen Journal NANO EXPRESS Open Access Anti-reflective nano- and micro-structures on 4H-SÌC for photodiodes Min-Seok Kang 1 Sung-Jae Joo2 Wook Bahng2 Ji-Hoon Lee1 Nam-Kyun Kim2 Sang-Mo Koo1 Abstract In this study nano-scale honeycomb-shaped structures with anti-reflection properties were successfully formed on SiC. The surface of 4H-SiC wafer after a conventional photolithography process was etched by inductively coupled plasma. We demonstrate that the reflection characteristic of the fabricated photodiodes has significantly reduced by 55 compared with the reference devices. As a result the optical response illumination dark of the 4H-SiC photodiodes were enhanced up to 178 which can be ascribed primarily to the improved light trapping in the proposed nano-scale texturing. Introduction Up to now silicon Si has been the dominant material for high-efficiency solar cells. However Si-based devices perform well only under the limited conditions of relatively low temperatures and power ranges. Alternatively in the research on wide-bandgap semiconductors silicon carbide SiC has shown considerable potential for both high-power and optoelectronic devices 1 . SiC exhibits a wide-bandgap 3.26 eV and superior thermal properties which are advantageous for high-temperature applications and solar energy conversion 2 . However polished SiC surfaces have a natural reflectivity with a strong spectral dependence. The reflectivity is inevitably high 20-40 due to the high refractive index of n 2.7-3.5 of SiC 3 . The optical losses associated with the reflectance of incident radiation are among the most important factors limiting the efficiency of a solar cell 4 . Therefore photovoltaic cells normally require special surface structures or materials which can reduce reflectance. A common solution is utilization of antireflection coatings based on .