Monolithic Light Emitting Diode Arrays using Gallium Phosphide

Abstract

THE high diode packing densities that can be achieved on single crystal slices of semiconductors mean that monolithic arrays of light emitters offer the possibility of displaying typescript signed characters from a 7 × 5 matrix, either for direct visual applications or for data recording. Previously this has only been achieved using the direct band gap semiconductors gallium arsenide and gallium arsenide phosphide, which emit radiation in the infrared or extreme red parts of the spectrum. Two problems have prevented gallium phosphide being used in monolithic arrays; they are the low electroluminescent efficiencies obtained from junctions formed by diffusion into indirect band gap materials and the lack of an adequate mask for use on gallium phosphide to define the diode areas during gaseous zinc diffusion.