Characterization of Silicon Nanowires Reflectance by Effective Index Due to Air-Silicon Ratio

• Published in: ECS transactions 2019-04, Vol.89 (4), p.17-30
• Main Authors: Koech, Philemon Kipsang, Ogini, Martins, Mohan, Susmitha, Alice Francis, Aneeta, Deo, Makarand, Albin, Sacharia, Sundaram, Kalpathy B.
• Format: Article
• Language: English
• ISSN: 1938-5862; 1938-6737; 1938-6737; 1938-5862
• DOI: 10.1149/08904.0017ecst

Silicon Nanowires (SiNWs) enhance light collection efficiency which is key in the performance of many optical and optoelectronic devices. We fabricated SiNWs by metal assisted chemical etching (MACE) and determined Air:Si ratios by analyzing SEM images of substrate surface by image thresholding technique in MATLAB. For normal incidence, a minimum reflectance of around 0.2% was achieved for about 2μm long SiNW with a slight increase when etching time was increased from 30 minutes to 45 minutes. Fresnel's equations at minimum reflectance provided an estimated effective refractive index (ERI) of 1.04. The Air:Si ratio decreased from 0.70 to 0.62 when the etching time was increased from 30 to 45 minutes which corresponded to an increase in the estimated ERI from 1.04 to 1.07. Beyond the etching time for minimum reflectance, the increase in reflectance may be due to increase in the ERI caused by the decreased Air:Si ratio.