Photoluminescence peak energy shifts under applied [110] and [100] uniaxial stress are interpreted within the framework of a multi-band Kohn–Luttinger model which takes into account the mixing of heavy, light, and spin-orbit split-off holes within the valence band. Experimental data are presented for 0.5&percent;, 1&percent;, and 1.7&percent;Si1−yCy/Sisamples which are best fitted with a conduction band offset of approximately 70&percent;. At this value of the conduction band offset, we show that small amounts of space charge induced band bending are required to explain the experimentally observed results. ©1998 American Institute of Physics.