Blueshifting of InGaAsP/InP laser diodes by low-energy ion implantation

Abstract

A new method based on low-energy implantation is presented for the fabrication of laser diodes with shifted emission wavelength. The laser diodes are based on InGaAsP/InGaAs/InP material, with compressively strained active layers. Low-energy implantation (18 keV As+) is used to generate vacancies near the surface of an incomplete laser structure, for which the epitaxial growth was interrupted 45 nm above the active layers of the device. The vacancies are subsequently diffused through the quantum wells by rapid thermal annealing. This diffusion causes a local intermixing of atoms at the interfaces of the active layers, which induces an increase of the band gap energy. The implantation/anneal process can be repeated several times to increase the amount of intermixing, thereby further shifting the emission wavelength. Once this process is completed, the upper optical confinement layer of the structure is overgrown using chemical beam epitaxy. Operational lasers with blueshifts as large as 35 nm were obtained.