Optical fiber communication systems have shifted toward the long wavelength range of 1.2-1.6 µm due to lower losses and dispersion available with high quality fibers. The quaternary GaInAsP/InP material system has evolved as the most promising system for light sources in this range.
Indium phosphide electronic devices are expected to possess high frequency switching capabilities, but present device technology is still rather primitive. In anticipation of future developments, which will render opto-electronic integration in this system advantageous, two laser structures on semi-insulating InP substrates were demonstrated. The substrate permits electrical isolation between components and thus is ideal in planar integration of the lasers with electronic devices.
Low threshold lasers can only be achieved when the active region is properly defined in two dimensions to provide good optical and carrier confinement. Present techniques usually require difficult and intricate growth step of two-step liquid phase epitaxy. Embedded epitaxy, by growth through a mask, offers a simple yet elegant means of two dimensional definition of the active region with only a single growth step. Low threshold lasers were fabricated with this technique and demonstrated its potential applications.
All GaInAsP/InP lasers show accelerated increase of threshold current with temperature of a different nature than similar GaA1As lasers. To understand the origin of this phenomenon, calculations were made of the Auger process in these lasers, and have demonstrated that they play a very important role in the temperature behavior of GaInAsP/InP lasers.
