Abstract
Here we propose an original waveguide-integrated plasmonic Schottky photodetector that takes full advantage of a thin metal stripe embedded entirely into a semiconductor. The photodetector is based on the long-range dielectric-loaded surface plasmon polariton waveguide with a metal stripe deposited on top of a semiconductor rib and covered by another semiconductor. As the metal stripe is entirely surrounded by semiconductor, all hot electrons with appropriate k-vectors can participate in transitions that highly enhances the electron transfer, and consequently the internal quantum efficiency. In addition, a high coupling efficiency from the photonic waveguide to the photodetector is simulated exceeding 90 % which enhances the external quantum efficiency. Calculations show that a responsivity exceeding 0.5 A/W can be achieved at telecom wavelength of 1550 nm and the bandwidth can exceed 100 GHz. Furthermore, it is shown that titanium nitride is a perfect material for the photodetector as it provides a low Fermi energy and long electron mean free path that enhance the hot electron transfer to the semiconductor. In addition, it shows reasonable metallic behavior and CMOS compatibility. Measurements showed that the Schottky barrier height between titanium nitride and p-doped silicon reaches 0.69–0.70 eV that matches the optimum signal-to-noise ratio operation calculated at 0.697 eV.
Highlights
Optical transceivers are the main building blocks of optical interconnects and consist of the laser light source, modulator,multiplexer, and photodetector[1,2,3]
For a metal stripe embedded in a dielectric there are two surface plasmon polariton (SPP), one on each side of the metal-dielectric interfaces that are bound to the metal interface, and with the electromagnetic energy located partially in the metal and in the dielectric
For the case of the metal stripe embedded into dielectric ridge it can be achieved by decreasing the metal stripe thickness below the penetration depth of the SPP into the metal, so the two SPP modes associated with two opposite interfaces can overlap and form a new SPP wave with an increased propagation range, the so called long-range dielectric-loaded SPP (LR-dielectric-loaded surface plasmon polariton (DLSPP))[23,24,25,26]
Summary
Optical transceivers are the main building blocks of optical interconnects and consist of the laser light source, modulator, (de)multiplexer, and photodetector[1,2,3]. Www.nature.com/scientificreports for a compact photonic waveguide-integrated germanium-on-insulator (GOI) photodetector where an internal quantum efficiency of 39%, corresponding to the responsivity of 0.41 A/W at 1 V bias voltage, was measured[9]. To enhance the efficiency of the IPE process it is desirable to confine the optical power at the metal boundary with the materials forming the Schottky barrier This will allow an increase in the interaction of light with the metal in very close vicinity of the interface where the photoemission process take place. Surface plasmons can decay either radiatively via emission of photons or non-radiatively through the generation of excited carriers, so called hot carriers The potential barrier can be overcome either directly or through quantum mechanical tunneling effects with the probability dependent on the barrier width and height as well as the charge carrier energy
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