Study of the interdiffusion effect on the band structures of Si_1-xGe_x/Si quantum wells

We investigated the influence of thermal interdiffusion on the band structures of Si_1-xGe_x/Si single quantum wells (SQWs) with a well width of 125 Å and Ge concentration x=0.3. Rapid thermal annealing with the temperatures of 750 and 800 °C leads to substantial interdiffusion indicated by a significant photoluminescence (PL) blueshift as large as 46 meV. The effect is modeled by a Si–Ge atomic interdiffusion at the heterointerface. The band structures and optical transitions of QW after interdiffusion were calculated based on an error function distribution and the 6+2-band k∙p method. The diffusion lengths of the intermixing process are deduced from the PL shift. The thermal dependence of the interdiffusion coefficients follows the Arrhenius law. An activation energy (E_a) for interdiffusion of 2.75 eV is obtained. Our investigation indicates that the 6+2-band k∙p formalism is valid for interdiffused Si_1-xGe_x/Si QWs.