Plasmonic Nanoslit Enhanced Metal-Semiconductor-Metal Photodetectors

We computationally show that metallic nanoslitsintegrated on Germanium metalsemiconductor-metal photodetectors show absorption enhancement up to 8 for TM-polarization in the communications C-band due to interference of horizontal surface plasmons. OCIS codes: 040.5160; 130.0250; 250.5403 Semiconductor industry has continuously scaled down electronic devices, significantly improving device level performance; but the same is not true for the on-chip electrical interconnections. The high frequency nature of photonics make optical interconnects a natural candidate for high capacity information transfer medium, resulting in an avalanching interest in demonstrating efficient Ge-based optical detection closely integrated with Silicon and Silicon based waveguide technologies to realize integrated optoelectronics [1-3]. It is desirable that the finger spacing and active layer thickness in metal-semiconductor-metal (MSM) photodetectors be reduced for high-speed operation while maintaining the efficiency of the device. Despite earlier reports in the literature on electromagnetic resonance modes in MSM structures [4,5], a complete study does not exist and there is a need for a thorough investigation of plasmonic gratings integrated with MSM photodetectors. For a proof-of-concept demonstration in the near infrared (NIR) photodetectors, we computationally studied Germanium based MSM photodetectors integrated with gold gratings as shown in Fig. 1. We computed the field Fig. 1. (a) MSM photodetector structure aeriel view (top) and cross-section along AB (bottom) (b) Simulated structure for allowed HSP modes with structural parameters. (c) Simulated structure for suppressed HSP modes. Fig. 2. (a) Far field transmission (normalized to source power) with and without HSP modes (b) E-field map for λi = 1550 nm and allowed HSP modes and (c) suppressed HSP modes (d) E-field map for λi = 2110 nm and allowed HSP modes and (e) suppressed HSP modes. E-field intensity values are clipped at 15 in the color scale. E-field intensity is normalized to the Efield intensity of the source. All fieldmaps use the same color scale. JWA39.pdf 1 9/30/2011 11:11:21 AM FIO/ LS Technical Digest @ 2011 OSA