Analysis of nano-grating-assisted light absorption enhancement in metal-semiconductor-metal photodetectors patterned using focused ion-beam lithography

Narottam K. Das, Edith Cowan University
Ayman Karar, Edith Cowan University
Mikhail Vasiliev, Edith Cowan University
Chee Leong Tan, Gwangju Institute of Science and Technology (GIST), Republic of Korea
Kamal Alameh, Edith Cowan University
Yong Tak Lee, Gwangju Institute of Science and Technology (GIST), Republic of Korea

NOTICE: this is the author’s version of a work that was accepted for publication in Optics Communications. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Optics Communications, 284, 6, (2011), 1694–1700. Original article available here


We present finite-difference time-domain (FDTD) analysis results of light absorption enhancement factor dependence on the profile shape of nano-gratings etched into the surfaces of metal–semiconductor–metal photodetector (MSM-PD) structures. The MSM-PDs patterned by nano-gratings are optimized geometrically, improving the light absorption near the design wavelength through plasmon-assisted electric field concentration effects. FDTD simulation results show about 50 times light absorption enhancement prediction for 850 nm light due to improved optical signal propagation through the nano-gratings in comparison with the conventional MSM-PD designs employing only a subwavelength aperture. We also report on the nano-grating profile shapes obtained typically in our experiments using focused ion-beam lithography and discuss the dependency of light absorption enhancement on the geometric parameters of nano-gratings inscribed into MSM-PDs. --------------------------------------------------------------------------------


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