Growth and characterization of Cd-Doped InGaAsP/InP double heterostructure lasers

The liquid phase epitaxial growth of Cd-doped InGaAsP/InP double heterostructure lasers (1.3 µm) has been studied. Cd has been found to have a smoothing effect on the morphology of the quaternary layers and a typical terracing effect on that of InP found also by doping with Zn. The defects, revealed by etching, were found to propagate in one to one correspondence from the substrate throughout the whole structure with no generation of defects even in a highly doped material. Electrical saturation at p ~2.10^l8Cm^-3 was found in InP by Hall measurements while no saturation was found in the quaternary up to a hole concentration of ~2.10^l9cm^-3. A lattice mismatch which is linearly dependent on the amount of Cd in the liquid was found by X-ray analysis. Cd was found to greatly facilitate the location of the p-n junction within the active region because of its low diffusion. Low threshold, very high external differential quantum efficiency, and high uniformity characterize the lasers made of this material. The results obtained in this work suggest that Cd should be considered as a promising candidate for a p-type dopant in fabrication of quaternary devices.