Method for fabricating a monocrystalline structure

Method for growing a monocrystalline target layer by epitaxy successively comprising:

• providing a substrate comprising a first monocrystalline layer made of silicon-germanium alloy, the first monocrystalline layer having a first surface covered by a protective oxide obtained by wet process oxidation of the first surface or obtained by thermal process, the first surface of the first monocrystalline layer having a degradation temperature at which the first surface roughens and forms dots,
• subjecting the protective oxide to plasma treatment to form a fluorinated salt and then eliminating the fluorinated salt by means of an anneal,
• inserting the substrate in a processing chamber at a loading temperature lower than the degradation temperature,
• subjecting the substrate to a temperature ramp from the loading temperature to an annealing temperature higher than the degradation temperature, wherein during the temperature ramp, a germanium precursor is inserted in the processing chamber between the loading temperature and the degradation temperature so as to deposit a monocrystalline buffer layer lattice matched with the first layer, the monocrystalline buffer layer being made from pure germanium
• annealing the first surface at a temperature higher than or equal to the annealing temperature in a hydrogen or nitrogen atmosphere, and
• depositing the monocrystalline target layer on the first surface by chemical vapor deposition, the monocrystalline target layer being lattice matched with the first monocrystalline layer, the monocrystalline buffer layer separating the monocrystalline target layer and the first layer.