CHARACTERIZATION OF GE SIGE STRAINED-BARRIER QUANTUM-WELL STRUCTURES USING PHOTOREFLECTANCE SPECTROSCOPY/

We have investigated Ge/SiGe strained-barrier quantum-well structures using photoreflectance spectroscopy. On the basis of the GAMMA-point t ransition energies associated with the Ge quantum well, the band offse t at the heterojunction between Ge and SiGe has been found to vary lin early with the germanium composition in the SiGe barrier layer. The co nduction-band-offset ratio Q(c)[=DELTAE(c)/(DELTAE(c) + DELTAE(vh))] a t the GAMMA point is estimated to be 0.68+/-0.08. From the intrinsic l inewidth of the quantum-well-related transitions, interface roughness has been characterized in this system and is estimated to be +/-1 mono layer in our samples.