Abstract
Optical electroabsorption modulators using quantum confinement Stark effect are important devices in optical commincation. Ge is group IV element that is compatible with Si process. It is possible to integrate Ge/SiGe quantum well devices with integrated circuite. In this thesis, we study the eigen state of carrier and analyze the electroabsorption in an asymmetric quantum well. We find out that if the barrier height of carriers in conduction band and valance band are different, there exists blue shift when electric field is applied. We further suggest a design rule for engineering the blue shift, and with this rule, we demonstrate an example of elctroabsorption modulators with Ge/SiGe asymmetric quantum well.