Using a standard RF-PECVD reactor, silicon layers are epitaxially grown at 175 C. Few µm thick layers can be efficiently used as an absorber in the wafer equivalent approach: p++ c-Si (wafer)/epi-Si (~ µm)/n+ aSi: H (12nm) has excellent diodes characteristics with FF of 80.5% and 8, 8% efficiency. By dilution of GeH4 in SiH4/H2 plasma, we show for the first time epitaxial SiGe alloys, with variable Ge fraction, grown at such low temperature. Structural and electronic properties of these materials has well has solar cells parameters are investigated using spectroscopic ellipsometry, Raman, TEM, J (V) characteristics and EQE. Using stress induced lift off technique ultra-thin Si layers of few cm2 are transferred on inexpensive substrates. Material quality is kept constant during the transfer process as shown by Raman FWHM of 5.3 cm-1, and ultra-thin heterojunctions solar cells are …