Design of a SiGe-Si quantum-well optical modulator

A light modulator consisting of modulation-doped SiGe-Si multiple quantum wells integrated in a silicon-on-insulator waveguide is designed. The device is based on the electrorefractive effect due to the variation of holes density in the SiGe wells, induced by applying a reverse bias on a PIN diode. This mechanism is simulated by numerical calculations of the hole distribution coupled with the optical guided mode propagation characteristics. The mode effective index variation of TE-polarized light at the 1.31-μm wavelength can then be obtained as a function of the applied bias. The influences of the structure parameters such as the thickness and the doping level of the doped barrier layers or the number of SiGe wells is analyzed thanks to a design of experiment method. The optimization gives an effective index variation of 2.10/sup -4/ for an applied bias voltage of 6 V. To obtain optical intensity modulation, this structure has to be included in a Fabry-Perot cavity. The modulation performances are analyzed.