Method for manufacturing a thick eptaxial layer of gallium nitride on a silicon or similar substrate and layer obtained using said method

A method for manufacturing, by means of epitaxy, a monocrystalline useful GaN layer on a substrate, the coefficient of thermal expansion of the substrate being less than the coefficient of thermal expansion of GaN such that the substrate is suitable for generating tensile strain in the useful GaN layer, the method comprising the following successive steps:

• (a) forming an AlN buffer layer on the substrate,
• (b) three-dimensionally epitaxially growing, directly on the AlN buffer layer, a GaN layer that is relaxed at the epitaxial temperature,
• (c1) epitaxially growing on the GaN layer a first intermediate layer having the composition BwAlxGayInzN, where w+x+y+z=1 and 0.5<x≦1, 0≦y<1, 0≦w<1 and 0≦z<1,
• (c2) epitaxially growing a layer having the composition BwAlxGayInzN, where w+x+y+z=1 and 0≦x<0.5, 0≦y<1, 0≦w<1 and 0≦z<1,
• (c3) epitaxially growing a second intermediate layer having the composition BwAlxGayInzN, where w+x+y+z=1 and 0.5<x≦1, 0≦y<1, 0≦w<1 and 0≦z<1,
• at least one of the layers formed in steps (c1) to (c3) being an at least ternary III-N alloy comprising aluminium and gallium,
• epitaxially growing the useful GaN layer.