A method of forming a Light Emitting Diode (LED) precursor comprising: forming a first semiconducting layer comprising a Group III-nitride on a substrate, selectively removing a portion of the first semiconducting layer to form a mesa structure, and forming a monolithic LED structure. According to the method, the first semiconducting layer has a growth surface on an opposite side of the first semiconducting layer to the substrate. According to the method, the first semiconducting layer is selectively removed to form the mesa structure such that the growth surface of the first semiconducting layer comprises a mesa surface and a bulk semiconducting surface. Further, the monolithic LED structure is formed on the growth surface of the first semiconducting layer such that the monolithic LED structure covers the mesa surface and the bulk semiconducting surface, the monolithic LED structure comprising a plurality of layers, each layer comprising a Group III-nitride, including a second semiconducting layer, an active layer provided on the second semiconducting layer, the active layer configured to generate light, and a p-type semiconducting layer provided on the active layer. A potential barrier is provided between a first portion of the p-type semiconducting layer covering the mesa surface and a second portion of the p-type semiconducting layer covering the bulk semiconducting surface. The potential barrier surrounds the first portion of the p-type semiconducting layer covering the mesa surface.