Photodetection in silicon beyond the band edge with surface states

TL;DR

This paper demonstrates silicon-based photodetectors operating beyond the band edge by utilizing surface state absorption, achieving notable responsivity and speed suitable for integrated optical applications.

Contribution

It introduces a novel silicon photodetector leveraging surface states for photodetection at telecom wavelengths, with measurable responsivity and high-speed operation.

Findings

Responsivity of 36 mA/W achieved

Quantum efficiency of 2.8% demonstrated

Photodetectors operate up to 60 MHz speed

Abstract

Silicon is an extremely attractive material platform for integrated optics at telecommunications wavelengths, particularly for integration with CMOS circuits. Developing detectors and electrically pumped lasers at telecom wavelengths are the two main technological hurdles before silicon can become a comprehensive platform for integrated optics. We report on the generation of free carriers in unimplanted SOI ridge waveguides, which we attribute to surface state absorption. By electrically contacting the waveguides, a photodetector with a responsivity of 36 mA/W and quantum efficiency of 2.8% is demonstrated. The photoconductive effect is shown to have minimal falloff at speeds of up to 60 Mhz.