monocrystalline layer for example an aln layer has to be inserted in the layer of gallium nitride or of the mixed nitride of gallium and another metal is completely independent of the substrate the preferred substrates were described above furthermore the process according to the invention may indifferently use any growth technique for deposition of the buffer layer the growth of deposits of gallium nitride or of the mixed nitride of gallium and another metal and for growth of the intermediate layer however the growth conditions of this layer must be such that it is monocrystalline therefore molecular beam epitaxy mbe already mentioned above or metalorganic chemical vapour deposition mocvd or hydride vapour phase epitaxy hvpe can also be used for growth of these layers and deposits the preferred process is mbe particularly under the conditions described below in which growth of a monocrystalline intermediate layer is possible temperature from 800 to 1000 u00b0 c and preferably from 900 to 950 u00b0 c and growth rate from 0 1 to 0 5 u03bcm h with the process according to the invention it is also possible to deposit several intermediate layers for example of aln in the gallium nitride layer or the layer of a mixed nitride of gallium and another metal in other words as mentioned in g steps d to f may be repeated for example between 1 and 5 times thus leading to the deposition of 2 to 6 intermediate monocrystalline layers therefore the process according to the invention is extremely flexible both from the point of view of choosing the substrate and the process for the growth of deposits and layers this is not.