The properties of long wavelength strained layer superlattice lasers grown by MOVPE

Abstract

The strain generated in strained layer superlattices (SLS’s) gives rise to a range of novel electronic and structural properties. These electronic properties could be used to either improve the performance of existing optoelectronic components or be exploited to create new devices. One such application is to enhance the efficiency and reliability of long wavelength lasers used in optical telecommunication systems. Such lasers are currently based on InP/InGaAsP lattice matched materials systems which emit at either 1.3 or 1.55 µm. It is believed that Auger recombination and inter-valence band absorption constitute the major mechanisms which limit the overall efficiency and determine threshold current of such devices. Biaxial strain, incorporated into strained layer su-perlattices, causes electronic band structure modifications which may suppress these non radiative loss mechanisms. Atmospheric pressure MOVPE growth of a long wave-length laser structure is described. The structure consists of an InxGa1−xAs/InyGa1−yAs SLS active region with InP cladding layers grown on InP (001). Structural analyses by transmission electron microscopy and x-ray double crystal diffraction have demon-strated that it is possible to grow high quality lasers based on this strained layer sys-tem. A range of structures which emitted at µ1.55 µm were grown and lased, at room temperature, under photoinjection. Equivalent threshold current densities, Jth, were typically in the range 1.5-6 kA/cm2 and high slope efficiencies, η, were achieved.