TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Heterostructure: In the heterostructure, the main portion of the active layer is inserted between a subjacent portion and a superjacent portion, and the subjacent and superjacent portions each comprise a concentration of dopants greater than 1017 cm-3, where the main portion, the subjacent portion and the superjacent comprise gallium nitride (GaN) and the dopant of the superjacent portion is different from the dopant of the subjacent layer; or the main portion of the active layer is inserted between a subjacent portion and a superjacent portion, and the material of the main portion is of a different AlxInyGa(1-x-y)N composition than the subjacent portion and the superjacent portion of the active layer, and the composition of the subjacent portion is different from the composition of the superjacent portion. Preferred Method: The method (M1) further involves implanting ions into the donor substrate to form an embrittlement zone at a depth that is equal to the thickness of the seed layer to be left on the support substrate after removing the portion of the donor substrate; measuring the surface roughness of the donor substrate and support substrate, and depositing a bonding layer on the surface of either or both substrates that have a roughness greater than 1 nm for a 5 micrometerx 5 micrometer surface measured by atomic force microscopy (AFM) and a peak valley surface topology of greater than or equal to 10 nm; epitaxially growing an active layer on the seed layer to a thickness of 3-100 micrometers without cracking to form a heterostructure; providing the active layer with a main portion whose thickness represents between 70 and 100% of the thickness of the active layer and whose concentration of dopants is less than or equal to 1017 cm-3; and choosing the material of the support substrate such that the coefficient of thermal expansion (CTE) of the support substrate material is between a minimum value that is less than 0.5x 10-6 K-1 below the CTE of the material of the main portion of the active layer and a maximum value that is not greater than 0.6x 10-6 K-1 above the CTE of the material of the main portion of the active layer at the temperatures used for epiaxially forming the active layer. The implanting is carried out after the formation of the bonding layer on the donor substrate, and through the bonding layer. Preferred Components: The support substrate has an electrical resistivity of less than 10-3 ohm.cm and a thermal conductivity of greater than 100 W.m-1.K-1. The support substrate comprises a refractory metal selected from tungsten (W), molybdenum (Mo), niobium (Nb) or tantalum (Ta) and their binary, ternary or quaternary alloys. The metal alloys are TaW, MoW, MoTa, MoNb, WNb or TaNb (preferably TaW comprising at least 45% tungsten or MoTa comprising more than 65% molybdenum). The bonding layer comprises a material comprising polycrystalline silicon, a silicide, a refractory metal, a metal boride, zinc oxide, or indium tin oxide; or a material having an electrical resistivity of less than or equal to 10-4 ohm.cm. The seed layer has an electrical resistivity of 10-3-0.1 ohm.cm. The seed layer and active layer comprise materials that provide a difference in lattice parameter of less than 0.005 Angstrom , and the active layer comprises a main portion in which the thickness represents between 70 and 100% of the thickness of the active layer and in which the concentration of dopant is less than or equal to 1017 cm-3. The support substrate comprises a material that provides a CTE that is between a minimum value that is less than 0.5x 10-6 K-1 below the CTE of the material of the main portion of the active layer and a maximum value that is not greater than 0.6x 10-6 K-1 above the CTE of the material of the main portion of the active layer at the temperatures used for epiaxially forming the active layer. The thickness of the main portion represents 100% of the thickness of the active layer and that the material of the main portion is of doped n type GaN, or the support substrate comprises molybdenum, the bonding layer is tungsten, and the seed layer is GaN. The seed layer comprises a monocrystalline material layer adapted for the epitaxial growth of a material of composition AlxInyGa(1-x-y)N. The active layer is a monocrystalline layer, and has a composition AlxInyGa(1-x-y)N. EXAMPLE - No suitable example given.