Properties of GaP Red-Emitting Diodes Grown by Liquid-Phase Epitaxy II. Effect of Substrate Orientation

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Abstract
Emission efficiency and reproducibility of GaP red-emitting diodes are improved by removal of a deteriorated layer of a p-type substrate by dissolution in the epitaxy solution just before growth of an n layer. Employment of this procedure enables investigating the effect of substrate orientation. The optimum tellurium concentration for diodes grown on (111)Ga surface of the substrate is 2∼2.5 times higher than that grown on (111)P surface, and the emission intensity at the optimum Te concentration is 1.5∼1.8 times stronger in the latter case. These results are explained by the difference in the impurity distribution near the p-n junction owing to out-diffusion of zinc atoms from the substrate into the epitaxial layer. An external quantum efficiency of 2.7% has been attained without antireflection coating by growing a tellurium and oxygen doped n layer on (111)P surface of a p-type substrate sufficiently etched by the epitaxy solution.