Extrinsic Photodiodes for Integrated Mid-Infrared Silicon Photonics

TL;DR

This paper demonstrates room-temperature mid-infrared silicon waveguide photodiodes using Zn doping, achieving high responsivity and low dark current, advancing integrated photodetectors for silicon photonics.

Contribution

First demonstration of room-temperature Zn-doped silicon waveguide photodiodes operating in the mid-infrared range.

Findings

Responsivity up to 87 mA/W at 2200-2400 nm

Dark current below 10 microamps

Effective mid-infrared detection at room temperature

Abstract

Silicon photonics has recently been proposed for a diverse set of applications at mid-infrared wavelengths, the implementation of which require on-chip photodetectors. In planar geometries, dopant-based extrinsic photoconductors have long been used for mid-infrared detection with Si and Ge acting as host materials. Leveraging the dopant-induced sub-bandgap trap-states used in bulk photoconductors for waveguide integrated mid-infrared detectors offers simple processing, integration, and operation throughout the mid-infrared by appropriate choice of dopant. In particular, Si doped with Zn forms two trap levels ~ 0.3 eV and ~ 0.58 eV above the valence band, and has been utilized extensively for cryogenically cooled bulk extrinsic photoconductors. In this letter, we present room temperature operation of Zn+ implanted Si waveguide photodiodes from 2200 nm to 2400 nm, with measured responsivities of up to 87 mA/W and low dark currents of < 10 microamps.