EFFECT OF SI-GE INTERDIFFUSION ON THE WAVE-GUIDE PROPERTIES OF SIGE-SI MQW PHOTODETECTOR

Because of Si-Ge interdiffusion in the Si-SiGe interface during the gr owth process, the square-wave refractive index distribution of a SiGe- Si multiple-quantum-web (MQW) will become smooth. In order to simulate the actual refractive index profile, a staircase approximation is app lied. Based on this approach, the dispersion equation of the MQW waveg uide is obtained by using a transfer matrix method, The effects of ind ex changes caused by the interdiffusion on the optical field and the c haracteristics of the photodetector are evaluated by solving the dispe rsion equation, It is shown that the Si-Ge interdiffusion can result i n a reduction of the effective absorption coefficient and the quantum efficiency.