Semiconductor light-emitting diodes have a layer stack consisting of semiconductor layers whose materials are specifically selected (with respect to base material and dopant) and are adapted to each other in order to set to a predetermined extent the optoelectronic properties and the electronic band structure within the individual layers and at the layer boundaries. At the transition between two adjacent, mutually complementarily doped light-emitting diode layers (p-doped and n-doped), an optically active zone is created which emits electromagnetic radiation when current flows through the semiconductor layer stack. The generated radiation is initially emitted in all directions, i.e., only partly in the emission direction of the semiconductor light-emitting diode. In order to reflect the proportion of the radiation emitted to the opposite side of the semiconductor layer stack back in the emission direction, an oxide layer, consisting of a transparent conductive oxide, and one or several mirror layers are provided behind the semiconductor layer stack. One portion of the electromagnetic radiation impinging upon the mirror layers is reflected depending upon the difference in the optical refractive indices of the layers, upon the conductivity of the mirror layer, upon the transparency of the oxide layer as well as upon the thickness of the oxide layer and of the preceding layers towards the optically active zone. In order to increase the reflected portion, conventionally in addition to the layer thicknesses primarily the material properties and material compositions of the respective layers are modified and optimised.
USPTO Backgrounds
USPTO Backgrounds