TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Method: The method further comprises: growing the second layer as a coherently strained second layer, within critical thickness limits for the second layer, forming the second layer, comprising etching the coherently strained second layer into segments having up to a 1000 mu m width, and (d) continuing growth of, or re-growing, the second layer, where the segments are merged or coalesced; repeating the steps (a)-(d) using the re-grown or coalesced second layer as the first layer in (a), where the segments comprise stripes, changing an orientation of the stripes of the layers in the subsequently deposited heterojunctions to obtain the two-dimensional relaxation, and gradually increasing or decreasing the lattice constants of the layers in the subsequently deposited heterojunctions; coalescing the segments with a coherently strained coalescence layer, where the coalescing is initiated by raising a temperature above a temperature used to grow the coherently strained coalescence layer prior to continuing the growth of the second layer; depositing mask material at a bottom or at a bottom and on a top of the segments to promote coalescence of the segments, and after the segments are merged, continuing growth of the second layer to overgrow masked areas masked by the mask material, thus forming a continuous at least partially relaxed second layer, or interrupting the growth, removing the mask material on the top of the segments, and continuing the growth of the second layer afterwards; growing the second layer as a coherently strained second layer, within critical thickness limits for the second layer, and forming the second layer, comprising etching the coherently strained second layer into a pattern of stripes resulting in at least partial relaxation of the coherently strained second layer into at least partially relaxed stripes having up to a 1000 mu m width, and re-growing the second layer, comprising growing a gallium nitride coalescence layer under one dimensional tensile strain on top of the stripe pattern, adopting an a-lattice constant of the stripes in the stripe pattern, and growing an indium gallium nitride layer on the gallium nitride coalescence layer, where the indium gallium nitride layer adopts the a-lattice constant of the stripes and results in one dimensional relaxation of the indium gallium nitride layer; patterning the indium gallium nitride layer into stripes with an angle of 30-90 degrees with respect to the stripes in the second layer, resulting in full or partial two dimensional relaxation of the indium gallium nitride layer; growing the second layer as a coherently strained indium gallium nitride second layer, within critical thickness limits for the second layer, on the first layer comprising gallium nitride, and forming the second layer, comprising etching the coherently strained second layer into a pattern of first stripes resulting in at least partial relaxation of the coherently strained second layer into at least partially relaxed stripes having up to a 1000 mu m width, and growing a first coalescence layer having a thickness of less than or equal to 20 nm and a different composition to the second layer, on top of the stripe pattern, patterning the first coalescence layer and the second layer into a pattern of second stripes with an angle of 30-90 degrees with respect to the first stripes in the second layer, resulting in formation of posts in the second layer and full or partial two dimensional relaxation of the second layer, coalescing the second stripes with a second coalescence layer having a thickness of less than or equal to 20 nm and growing an indium gallium nitride layer on the second coalescence layer, where the indium gallium nitride layer adopts the lattice constant of the posts and has a different material composition to the second coalescence layer; growing the second layer as a coherently strained second layer, within critical thickness limits for the second layer, and forming the second layer, comprising etching the coherently strained second layer into a pattern of segments resulting in at least one-dimensional or two-dimensional partial relaxation of the coherently strained second layer into at least partially relaxed segments having up to a 1000 mu m width, and continuing growth of, or re-growing, the second layer, where the segments are merged or coalesced; growing the second layer comprising a coherently strained second layer, within critical thickness limits for the second layer, and forming the second layer, comprising etching the coherently strained second layer into segments resulting in at least partial relaxation of the coherently strained second layer into at least partially relaxed segments having up to a 1000 mu m width, and merging the segments by growing a coalescence layer composed of a material with a different composition than the coherently strained second layer; obtaining the first layer comprising a gallium nitride layer, depositing a mask material on the gallium nitride layer, where the mask material includes openings having a width up to 1000 mu m, growing and forming the second layer comprising a relaxed III-nitride pillar (504) in each of many openings, to form many III-nitride pillars, where the relaxed III-nitride pillars include indium and/or gallium, and continuing growth of the III-nitride pillars, where the III-nitride pillars overgrow the openings to form a relaxed III-nitride film including indium and/or gallium, where (a1) the gallium nitride layer and the relaxed III-nitride film have a same lattice structure but different lattice constants, (b1) the gallium nitride layer and the relaxed III-nitride film form a heterojunction, and (c1) the heterojunction forms an active area of a device or serves as a pseudo-substrate for the device; obtaining the first layer comprising a gallium nitride layer, and growing and forming the second layer comprising growing a many relaxed III-nitride pillars on the gallium nitride (gallium nitride) layer, where the relaxed III-nitride pillars include indium and/or gallium, and the relaxed III-nitride pillars are selectively seeded on the gallium nitride layer and have a width up to 1000 mu m, continuing growth of the relaxed III-nitride pillars, where the relaxed III-nitride pillars are merged, to form a relaxed III-nitride film including indium and/or gallium, where (a1)-(c1) as above per se; (a2) obtaining the first layer comprising a III-nitride or gallium nitride base layer, (b2) growing the second layer comprising depositing a strained indium gallium nitride of formula (InxGa(1-x)N) (I) layer on top of the III-nitride or gallium nitride base layer, depositing an indium gallium nitride of formula (InyGa(1-y)N) (II) layer on layer (I) to form a two layer stack, where layer (II) is thicker than the layer (I) and y is greater than x, (c2) etching the two layer stack with a pattern to form etched features, (d2) selectively etching the thinner layer (I) only, undercutting the thicker layer (II) in such a way that only a post remains, where the thicker layer (II) is detached from the base layer so that it can relax and adopt its unstrained lattice constant, and (e2) growing an indium gallium nitride of formula (InzGa(1-z)N) (III) layer on top of layer(II); repeating steps (a2)-(e2) as above per se, where layer (III) is the base layer for the next step (a2), the strained layer (I) in the next step (a2) is an indium gallium nitride of formula (InsGa(1-s)N) (IV) layer, the thicker layer (II) in the next step (b2) is an indium gallium nitride of formula (Int(Ga(1-t)N) layer, where s is greater than t such that (IV) layer and the (V) layer form a coherently strained stack, the etching in the next step (c2) is with the pattern comprising second stripes oriented in a second direction, the (III) layer in the next growing step (e2) is fully relaxed (for y is equal to t which is equal to z), or partially relaxed in the presence of small differences between y, t, and z, and x, y, z, t are compositions of indium in the indium gallium nitride layers; obtaining the first layer comprising a III-nitride or gallium nitride base layer, forming nano or micron sized or width openings on a surface of a gallium nitride or III-nitride base layer, growing the second layer comprising depositing a strained (I) layer into the openings only, depositing (II) layer on the (I) layer to form a two layer stack, where (II) layer is thicker than the (I) layer and y is greater than x, selectively etching the thinner (I) layer only, undercutting the thicker (II) layer in such a way that only a nanometer sized post remains supporting the thicker (II) layer, and growing (III) layer on top of (II); growing the second layer comprising an indium gallium nitride bulk base layer, and growing an indium gallium nitride active region coherently on or above the indium gallium nitride bulk base layer, where a thickness and indium composition of the indium gallium nitride active region are larger than a thickness and indium composition of an indium gallium nitride active region that is not grown on the indium gallium nitride bulk base layer, and the indium gallium nitride bulk base layer is at least partially relaxed, and has at least one lattice constant that match at least one lattice constant of the indium gallium nitride active region grown on the indium gallium nitride bulk base layer; growing the second layer comprising an n-type indium gallium nitride base layer deposited on the first layer comprising a substrate, and growing an indium gallium nitride active region coherently on or above the indium gallium nitride bulk base layer, where a thickness and indium composition of the active region are larger than a thickness and indium composition of an indium gallium nitride active region that is not grown on the indium gallium nitride bulk base layer, and the indium gallium nitride bulk base layer is at least partially relaxed, and has at least one lattice constant that match at least one lattice constant of the indium gallium nitride active region grown on the indium gallium nitride bulk base layer, and a p-type indium gallium nitride layer deposited on or above the indium gallium nitride active region; patterning the indium gallium nitride on the gallium nitride substrate, and relaxed indium gallium nitride on the patterned indium gallium nitride, where the indium gallium nitride bulk base layer comprises the relaxed indium gallium nitride and the active region is deposited on the relaxed indium gallium nitride; and repeating the steps (a)-(d) using the re-grown or coalesced second layer as the first layer in (a) and gradually decreasing or stepping down the lattice constants of the layers in the subsequently deposited heterojunctions. The etched features are merged by growth of (III), leading to a relaxed (z equals to y) or partially relaxed (z not equal to y) film (III) with a lattice constant corresponding to the patterned relaxed (II) features. In the method adjacent (II) features in the stacks are merged by growth of the (III), leading to a relaxed (z equals to y) or partially relaxed (z not equal to y) (III) film with a lattice constant corresponding to the patterned relaxed (II) features. Preferred Components: The first layer is gallium nitride and the second layer is a nitride containing indium and/or gallium, or aluminum and/or gallium. The pattern comprises first stripes oriented in a first direction. The second layer comprises at least one quantum well. EXAMPLE - No suitable example given.