Enhancement of photocurrent in ultrathin active-layer photodetecting devices with photonic crystals

Abstract

We demonstrate an enhancement of the photoelectric-conversion efficiency of an ultrathin (50 nm) silicon active-layer photodetecting device using a two-dimensional photonic crystal positioned nearby to boost the optical absorption. We show both experimentally and with simulations that the incident-light absorption within the active layer is enhanced by optical-resonance effects at the photonic band edge. We also find that a photonic crystal with deeper holes can lead to an even larger absorption enhancement due to better quality (Q)-factor matching between the photonic band-edge modes and the intrinsic material absorption. The experimentally observed photocurrent of the fabricated photonic-crystal sample is increased by a factor of ∼20 at the photonic band-edge wavelength relative to that of a control sample without the photonic crystal which is attributed to the improved Q matching. © 2012 American Institute of Physics.