Linear Optical Response of Si_(1-x)Ge_x Compounds

摘要

Si_(1-x)Ge_x is a good candidate as a substitute material for Si in a low-power andhigh-speed semiconductor device technologies. Optical devices, such as heterojunction bipolartransistors, are already in industrial production. The samples are grown on Si(001) with both nandp-type impurities and with different Ge concentrations. The linear optical response of Si1-xGex is investigated theoretically using a full-potential linearized augmented plane wave methodwith respect to composition x. The calculated real and imaginary parts of the dielectric functionε(ω) = ε1(ω) + iε2(ω) were found to be in good agreement with recent spectroscopic ellipsometrymeasurements performed by Bahng et al., J. Phys.: Condens. Matter 13, 777 (2001). We alsoperform absorption measurements for different type of samples showing the variation of energygaps as a function of Ge concentrations.