In this work, we study the morphology, composition and optical properties of AlGaN epilayers grown by plasma-assisted molecular beam epitaxy on the AlN buffer layer which was performed on regular Si substrate and compliant Si substrate with a preformed buffer porous silicon layer (por-Si) and carbonized porous layer(SiC/por-Si). The AlGaN layers formed on the por-Si buffer revealed a 15% higher intensity of photoluminescence spectra in visible range in comparison with ones formed on regular Si substrate.