A study of far-field patterns from high performance 1.3-µm InGaAsP-InP edge-emitting LED's

Liquid-phase epitaxy InGaAsP-InP 1.3-µm edge-emitting LED's are fabricated with a very simple Schottky-delineated stripe structure. With a stripe 50 µm wide and 200-250 µm long, typical characteristics of these devices include 170 µW of optical power coupled into a 60-µm core 0.2-NA graded index fiber, 600-Å spectral halfwidths, 2-5-ns risetimes. Unlike GaAs-GaAlAs edge-emitting LED's, best results of coupling efficiency are obtained with InGaAsP-InP LED's whose active layer thickness is in the range 0.12-0.15 µm, due to asymmetry in the far-field patterns. Our study of these far-field patterns shows that this asymmetry is governed by the quality of the active layer material located near the InGaAsP-nInP hetero-interface.