A structure comprising an epitaxial group-III-nitride buffer-layer structure (100, 200, 500) between a silicon substrate (110, 210, 310, 510) and at least one active layer, wherein the buffer-layer structure (100, 200, 500) comprises at least one stress management layer sequence including an interlayer structure (130, 230, 330, 530) arranged between and adjacent to a first and a second group-III-nitride layer (120, 140, 220, 240, 320, 340, 520, 540), wherein the interlayer structure (130, 230, 330, 530) comprises a group-III-nitride interlayer material having a larger band gap than the materials of the first and second group-III-nitride layers (120, 140, 220, 240, 320, 340, 520, 540), and wherein a p-type-dopant-concentration profile drops, starting from at least 5×10 18 cm -3, by at least a factor of two in transition from the interlayer structure (130, 230, 330, 530) to the first and second group-III-nitride layers (120, 140, 220, 240, 320, 340, 520, 540), wherein the thickness of the first group-III-nitride layer (120, 220, 320, 520) is between 300 nm and 2000 nm, and the thickness of the second group-III-nitride layer (140, 240, 340, 540), is between 300 nm and 1500 nm, wherein the dopant concentration of the first group-III-nitride layer (120, 220, 320, 520) and of the second group-III-nitride layer (140, 240, 340, 540) is not more than 1×10 17 cm -3, wherein the dopant concentration throughout the interlayer structure (130, 230, 330, 530) is at least 5×10 18 cm -3, the interlayer structure (130, 230, 330, 530) comprises three different layers, a first group-III-nitride interlayer arranged between and adjacent to a second and a third group-III-nitride interlayer (535, 536, 537), wherein the thickness is between 20 nm and 200 nm for second and a third group-III-nitride interlayer (536, 537), the second and third group-III-nitride interlayers (536, 537) are made of GaN as well as the first and second group-III-nitride layers (120, 140, 220, 240, 320, 340, 520, 540) and wherein the first group-III-nitride interlayer consist of AlGaN and the first group-III-nitride interlayer comprises a constant aluminum content or comprises a gradient in the aluminum content increasing from the second group-III-nitride interlayer to the third group-III-nitride interlayer, wherein the second group-III-nitride interlayer is closer to the substrate than the third group-III-nitride interlayer. wherein the thickness of the first group-III-nitride layer (120, 220, 320, 520) is between 300 nm and 2000 nm, and the thickness of the second group-III-nitride layer (140, 240, 340, 540), is between 300 nm and 1500 nm, wherein the dopant concentration of the first group-III-nitride layer (120, 220, 320, 520) and of the second group-III-nitride layer (140, 240, 340, 540) is not more than 1×10 17 cm -3, wherein the dopant concentration throughout the interlayer structure (130, 230, 330, 530) is at least 5×10 18 cm -3, the interlayer structure (130, 230, 330, 530) comprises three different layers, a first group-III-nitride interlayer arranged between and adjacent to a second and a third group-III-nitride interlayer (535, 536, 537), wherein the thickness is between 20 nm and 200 nm for second and a third group-III-nitride interlayer (536, 537), the second and third group-III-nitride interlayers (536, 537) are made of GaN as well as the first and second group-III-nitride layers (120, 140, 220, 240, 320, 340, 520, 540) and wherein the first group-III-nitride interlayer consist of AlGaN and the first group-III-nitride interlayer comprises a constant aluminum content or comprises a gradient in the aluminum content increasing from the second group-III-nitride interlayer to the third group-III-nitride interlayer, wherein the second group-III-nitride interlayer is closer to the substrate than the third group-III-nitride interlayer.