A light-emitting device; comprising: a conductive support structure comprising Cu; a GaN-based semiconductor structure disposed on the conductive support structure, wherein the GaN-based semiconductor structure comprises a p-type GaN-based layer, a GaN-based active layer and an n-type GaN-based layer, wherein the GaN-based semiconductor structure has a first semiconductor surface which is a surface of the n-type GaN-based layer, a side semiconductor surface and a second semiconductor surface which is a surface of the p-type GaN-based layer, wherein the first semiconductor surface, relative to the second semiconductor surface, is proximate to the conductive support structure, wherein the second semiconductor surface is opposite to the first semiconductor surface, and wherein a thickness of the GaN-based semiconductor structure is less than 5 microns; a p-type electrode electrically connected to the p-type GaN-based layer; and an n-type electrode electrically connected to the n-type GaN-based layer, wherein the n-type electrode has a first electrode surface, a side electrode surface and a second electrode surface, wherein the first electrode surface, relative to the second electrode surface, is proximate to the semiconductor structure, and wherein the second electrode surface is opposite to the first electrode surface, a passivation layer disposed on the side semiconductor surface and the second semiconductor surface, wherein the passivation layer comprises a first portion contacting the p-type GaN-based layer, a second portion contacting the GaN-based active layer, a third portion contacting the n-type GaN-based layer, a fourth portion contacting the side electrode surface, and a fifth portion contacting the second electrode surface, and wherein the passivation layer is partially arranged between the semiconductor structure and the conductive support structure, wherein the said first to fifth portions of the passivation layer and the portion thereof arranged between the semiconductor structure and the conductive support structure are formed of a continuous layer. a conductive support structure comprising Cu; a GaN-based semiconductor structure disposed on the conductive support structure, wherein the GaN-based semiconductor structure comprises a p-type GaN-based layer, a GaN-based active layer and an n-type GaN-based layer, wherein the GaN-based semiconductor structure has a first semiconductor surface which is a surface of the n-type GaN-based layer, a side semiconductor surface and a second semiconductor surface which is a surface of the p-type GaN-based layer, wherein the first semiconductor surface, relative to the second semiconductor surface, is proximate to the conductive support structure, wherein the second semiconductor surface is opposite to the first semiconductor surface, and wherein a thickness of the GaN-based semiconductor structure is less than 5 microns; a p-type electrode electrically connected to the p-type GaN-based layer; and an n-type electrode electrically connected to the n-type GaN-based layer, wherein the n-type electrode has a first electrode surface, a side electrode surface and a second electrode surface, wherein the first electrode surface, relative to the second electrode surface, is proximate to the semiconductor structure, and wherein the second electrode surface is opposite to the first electrode surface, a passivation layer disposed on the side semiconductor surface and the second semiconductor surface, wherein the passivation layer comprises a first portion contacting the p-type GaN-based layer, a second portion contacting the GaN-based active layer, a third portion contacting the n-type GaN-based layer, a fourth portion contacting the side electrode surface, and a fifth portion contacting the second electrode surface, and wherein the passivation layer is partially arranged between the semiconductor structure and the conductive support structure, wherein the said first to fifth portions of the passivation layer and the portion thereof arranged between the semiconductor structure and the conductive support structure are formed of a continuous layer.