We report epitaxial growth of compressively strained silicon directly on (100) silicon substrates by plasma-enhanced chemical vapor deposition. The silicon epitaxy was performed in a silane and hydrogen gas mixture at temperatures as low as 150°C. We investigate the effect of hydrogen dilution during the silicon epitaxy on the strain level by high-resolution x-ray diffraction. Additionally, triple-axis x-ray reciprocal-space mapping of the samples indicates that (i) the epitaxial layers are fully strained and (ii) the strain is graded. Secondary-ion mass spectrometry depth profiling reveals the correlation between the strain gradient and the hydrogen concentration profile within the epitaxial layers. Furthermore, heavily phosphorus-doped layers with an electrically active doping concentration of ~2 × 1020 cm−3 were obtained at such low growth temperatures.