Method for forming a highly relaxed epitaxial semiconductor layer (52) with a thickness between 100 nm and 800 nm in a growth chamber includes four principle steps. In a first step, the method provides a substrate (51) in the growth chamber on a substrate carrier. In a second step, the method maintains a constant substrate temperature (TS) of the substrate (51) in a range between 350° C. and 500° C. In a third step, the method establishes a high-density, low-energy plasma in the growth chamber such that the substrate (51) is being exposed to the plasma. In a fourth step, the method directs Silane gas (SiH4) and Germane gas (GeH4) through the gas inlet into the growth chamber, the flow rates of the Silane gas and the Germane gas being adjusted in order to form said semiconductor layer (52) by means of vapor deposition with a growth rate in a range between 1 and 10 nm/s. The semiconductor layer (52) has a Germanium concentration x in a range between 0