Green luminescence efficiency in gallium phosphide

Abstract

The present understanding of the operation of green-emitting GaP LEDs is reviewed. All existing visible LED devices which are made in III-V compound semiconductors are inefficient. In green-luminescent GaP this inefficiency is becoming understood, and quantitative analyses of the important mechanisms are described. The radiative processes include free-exciton and bound-exciton recombination which are important in p-type and n-type material with and without nitrogen doping, but in all materials the recombination is dominated by non-radiative processes which have proved to be elusive and difficult to eliminate. Particular emphasis is therefore placed on recent advances in the quantitative classification of these dominant non-radiative processes in n-type material. These are: (1) recombination at deep defect levels positioned approximately 0.75 eV from the valence band, (2) diffusion-limited recombination at dislocations, and (3) surface and interface recombination.