Novel Silicon-Carbon (Si:C) Schottky Barrier Enhancement Layer for Dark-Current Suppression in Ge-on-SOI MSM Photodetectors

This letter reports the first demonstration of an evanescent coupled germanium-on-silicon-on-insulator (Ge-on-SOI) metal-semiconductor-metal (MSM) photodetector with a novel silicon-carbon (Si:C) Schottky barrier enhancement layer. Through the insertion of a Si:C barrier layer between the metal/Ge interface, the hole Schottky barrier height phi_bh can effectively be enhanced to ~0.52 eV above the valence band edge. As a result, significant dark-current I_Dark suppression by more than four orders of magnitude was demonstrated, leading to an impressive I_Dark of ~11.5 nA for an applied bias V_A of 1.0 V. Optical measurements performed at a photon wavelength of 1550 nm revealed the achievement of good internal responsivity and quantum efficiency of ~530 mA/W and 42.4%, respectively, making such a high-performance Ge-on-SOI MSM photodetector a promising option for optical communication applications.