A GaN based Light Emitting Diode comprising: a substrate, a light emitting structure comprising: an N cladding layer, an active region, and a P cladding layer, a window structure (13, 109, 110, 111) grown on said P cladding layer, an N electrode in ohmic contact with said N cladding layer, and a P electrode in ohmic contact with said P cladding layer, wherein: said window structure comprises a thin, transparent, conductive outer layer having an exposed surface with four sides; and the complementary pair of P and N electrodes (113; 115) are formed along opposing sides of said exposed surface, characterised in that said P electrode is formed on said exposed surface and has a T-shape when viewed from the top, with a head of the T-shape being a bar formed along one side of said exposed surface, and a leg of the T-shape being a semi-circular portion which joins the bar; said P electrode is formed of a layer of Ti which passes through the conductive outer layer and wherein an Au bond pad is formed on and in the form of, the Ti electrode; and said N electrode comprises a bond pad assembly formed on said N cladding layer through an aperture located at the middle of the side of the face opposite to said one side. a substrate, a light emitting structure comprising: an N cladding layer, an active region, and a P cladding layer, an N cladding layer, an active region, and a P cladding layer, a window structure (13, 109, 110, 111) grown on said P cladding layer, an N electrode in ohmic contact with said N cladding layer, and a P electrode in ohmic contact with said P cladding layer, wherein: said window structure comprises a thin, transparent, conductive outer layer having an exposed surface with four sides; and the complementary pair of P and N electrodes (113; 115) are formed along opposing sides of said exposed surface, characterised in that said P electrode is formed on said exposed surface and has a T-shape when viewed from the top, with a head of the T-shape being a bar formed along one side of said exposed surface, and a leg of the T-shape being a semi-circular portion which joins the bar; said P electrode is formed of a layer of Ti which passes through the conductive outer layer and wherein an Au bond pad is formed on and in the form of, the Ti electrode; and said N electrode comprises a bond pad assembly formed on said N cladding layer through an aperture located at the middle of the side of the face opposite to said one side. said window structure comprises a thin, transparent, conductive outer layer having an exposed surface with four sides; and the complementary pair of P and N electrodes (113; 115) are formed along opposing sides of said exposed surface, characterised in that said P electrode is formed on said exposed surface and has a T-shape when viewed from the top, with a head of the T-shape being a bar formed along one side of said exposed surface, and a leg of the T-shape being a semi-circular portion which joins the bar; said P electrode is formed of a layer of Ti which passes through the conductive outer layer and wherein an Au bond pad is formed on and in the form of, the Ti electrode; and said N electrode comprises a bond pad assembly formed on said N cladding layer through an aperture located at the middle of the side of the face opposite to said one side.