SiGe Bandgap Tuning for High Speed Eam

Abstract

We report bandgap engineering of Ge rich SiGe rib waveguides between 1550 nm and 1580 nm through an annealing process. The insertion loss of the material (transmission spectrum) is analysed between 1520 nm and 1600 nm. The experimental data are elaborated by implementing the Tauc Method analysis, and the material bandgap estimation is calculated. A maximum blue shift of 38 nm, with an overall reduction of Si content, suggests that the diffusion of Si in the Ge seed layer during anneal improves the homogeneity of the growth layer. The proposed technique provides a path for tailoring the operational wavelength of devices such as electro-absorption modulators, realized on an SOI platform.

56 Gbps Si/GeSi integrated EAM

“…Through the use of Ge and GeSi, Electro Absorption Effect based modulators [21]- [23] (Franz-Keldysh Effect [24], [25] in bulk for the C/L-band and the Quantum Confined Stark Effect [26] in quantum well materials for the O to C Band) offer the best trade-offs in terms of speed, footprint and power consumption for highly integrated Si-PICs and short/medium-haul applications. For bulk FK based modulators, Thermal Anneal [27] (RTA) or Rapid Melt Growth [28], [29] (RMG) techniques can be used to integrate arrays of modulators working at different bandgap energy or wavelengths by tuning of the material composition. These techniques offer the potential to overcome the limited optical bandwidth (~35 nm) of this class of modulators.…”

“…For this first prototype the presence of the Ge buffer layer is responsible for a higher IL, due to background and undesirable absorption in the wavelength range of interest. Insertion Loss can be improved by using Rapid Thermal Anneal [27] before the device is realized to diffuse silicon into the Ge buffer layer to obtain a homogenous GeSi layer, or growing GeSi layer with epitaxial techniques that do not require any Ge buffer layer [28], [29] .…”