A structure including a compressively strained semiconductor layer, the compressively strained layer having a strain greater than or equal to 0.25%. A tensilely strained semiconductor layer may be formed over the compressively strained layer. The compressively strained layer is substantially planar, having a surface roughness characterized in (i) having an average wavelength greater than an average wavelength of a carrier in the compressively strained layer and/or (ii) having an average height less than 10 nm.