A light emitting device comprising - a body comprising a substrate of a semiconductor material of a first doping kind of a first doping concentration (p); - an isolation layer adjacent the substrate; - the substrate having an upper surface and having formed therein on one side of the upper surface: - a first island of a second doping kind of a second doping concentration (n +) to form a first junction between the first island and the substrate, the first island having an upper surface (16.1); - a second island of a third doping kind of a third doping concentration (n +) spaced laterally from the first island, so that the first island has a first face (16.2) and the second island has a second face (18.2), the first and second faces extending from the upper surface on the one side of the upper surface and mutually facing one another, and the second island having an upper surface (18.1); - the substrate providing a laterally extending link between the first face and the second face, the link comprising: - an upper surface coinciding with the upper surface of the substrate, so that the upper surface of the link, the upper surface (16.1) of the first island and the upper surface (18.1) of the second island collectively form a planar interface between the body and the isolation layer; and - first and second opposed sidewalls (20.1, 20.2), each of the first and second sidewalls of the link extending from the upper surface on the one side of the upper surface from the first face (16.2) of the first island to the second face (18.2) of the second island and being terminated by a region (19.1) of the isolation layer; - a terminal arrangement connected to the body and configured to apply a reverse bias to the first junction to cause a breakdown mode of the first junction, thereby to cause the device to emit light; and - a region configured to facilitate the transmission of the emitted light, the region extending on another side of the upper surface of the substrate perpendicularly away from a zone comprising at least one of the first face (16.2) and at least part of a depletion region extending from the first face (16.2) into the link. - a body comprising a substrate of a semiconductor material of a first doping kind of a first doping concentration (p); - an isolation layer adjacent the substrate; - the substrate having an upper surface and having formed therein on one side of the upper surface: - a first island of a second doping kind of a second doping concentration (n +) to form a first junction between the first island and the substrate, the first island having an upper surface (16.1); - a second island of a third doping kind of a third doping concentration (n +) spaced laterally from the first island, so that the first island has a first face (16.2) and the second island has a second face (18.2), the first and second faces extending from the upper surface on the one side of the upper surface and mutually facing one another, and the second island having an upper surface (18.1); - a first island of a second doping kind of a second doping concentration (n +) to form a first junction between the first island and the substrate, the first island having an upper surface (16.1); - a second island of a third doping kind of a third doping concentration (n +) spaced laterally from the first island, so that the first island has a first face (16.2) and the second island has a second face (18.2), the first and second faces extending from the upper surface on the one side of the upper surface and mutually facing one another, and the second island having an upper surface (18.1); - the substrate providing a laterally extending link between the first face and the second face, the link comprising: - an upper surface coinciding with the upper surface of the substrate, so that the upper surface of the link, the upper surface (16.1) of the first island and the upper surface (18.1) of the second island collectively form a planar interface between the body and the isolation layer; and - first and second opposed sidewalls (20.1, 20.2), each of the first and second sidewalls of the link extending from the upper surface on the one side of the upper surface from the first face (16.2) of the first island to the second face (18.2) of the second island and being terminated by a region (19.1) of the isolation layer; - an upper surface coinciding with the upper surface of the substrate, so that the upper surface of the link, the upper surface (16.1) of the first island and the upper surface (18.1) of the second island collectively form a planar interface between the body and the isolation layer; and - first and second opposed sidewalls (20.1, 20.2), each of the first and second sidewalls of the link extending from the upper surface on the one side of the upper surface from the first face (16.2) of the first island to the second face (18.2) of the second island and being terminated by a region (19.1) of the isolation layer; - a terminal arrangement connected to the body and configured to apply a reverse bias to the first junction to cause a breakdown mode of the first junction, thereby to cause the device to emit light; and - a region configured to facilitate the transmission of the emitted light, the region extending on another side of the upper surface of the substrate perpendicularly away from a zone comprising at least one of the first face (16.2) and at least part of a depletion region extending from the first face (16.2) into the link.