Type I Band Alignment inSi1−xGex/Si(001)Quantum Wells: Photoluminescence under Applied [110] and [100] Uniaxial Stress

We present experimental verification of a type I conduction band alignment for coherently strained ${\mathrm{Si}}_{1-x}{\mathrm{Ge}}_x$ layers in (001) silicon, with $0.15\le x\le 0.38$. A novel substrate bending scheme is used to apply in-plane uniaxial compressive and tensile stress along the [100] and [110] directions. Band edge photoluminescence from SiGe and Si is shifted with stress in accordance with deformation potential theory. Tensile stress along [110] allows clear distinction between types I and II band alignment where the predicted shifts are in opposite directions.