Electron leakage in 1.5-μm InGaAsP separate confinement heterostructure lasers

Abstract

The extent of electron leakage in λ=1.55 μm InGaAsP separate confinement heterostructure (SCH) lasers, and its dependence on the p-buffer layer crystal composition, have been studied both experimentally and theoretically. A significant difference was observed between the light output characteristics of 1.55-μm SCH lasers with λ≡1.3 buffer layers fabricated by a one-stage liquid phase epitaxy growth process and those produced by a two-step technique, suitable for the fabrication of distributed feedback lasers, comprising liquid phase epitaxy and metalorganic chemical vapor deposition. These observations are attributed to the poor electron confinement in SCH lasers with λ≡1.3 μm buffer layers which is compounded by the introduction of nonradiative interfacial recombination centers by the interruption of the growth procedure. Bulk recombination in the p-buffer layer is shown to be a problem for buffer layer compositions of lower band gaps and a composition of λ≡1.2 μm is determined to be a good compromise between electron confinement and optical wave interaction.