Design and Simulations of Ge₂Sb₂Te₅ Vertical Photodetector for Silicon Photonic Platform

Abstract

Here, we report design and simulations of a vertical photodetector based on amorphous Ge <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Sb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Te <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sub> (a-GST) for silicon platform at telecommunication wavelength (1550 nm). In our investigations, it is found that a-GST on silicon platform can be used as a waveguide photodetector with good responsivity and low dark current. Optimization of the structure is done to improve absorption, photocurrent, and corresponding electrical current at cathode. Our investigations reveal that ~150 nm is optimized thickness of a-GST material for high responsivity (~48 A/W) when integrated on top of a single-mode silicon-on-insulator waveguide. This responsivity is comparable with existing avalanche photodiodes. With optimized dimensions, a good ratio of photocurrent to dark current is obtained. To the best of our knowledge, this is the first report on a-GST-based photodetector.