MOCVD-grown dilute nitride type II quantum wells (Invited paper)

Dilute nitride Ga(In)NAs/GaAsSb "W" type II quantum wells on GaAs substrates have been grown by metal-organic chemical vapor deposition (MOCVD). Design studies underscore the importance of nitrogen incorporation to extend the emission wavelength into the 1.5 mu m region as well as increase the electron confinement, given the material strain relaxation limitations. These studies also indicate that the Sb content of the GaAs1-xSbx hole well is required to be greater than x similar to 0.2, to provide adequate hole confinement (i.e., Delta E-v > 150 meV). Photoluminescence (PL) and electroluminescence (EL) studies are used to characterize the optical transitions and compare with a ten-band k.p simulation. We find that the lowest energy type II transition observed is in good agreement with theory. Preliminary results are presented on diode lasers with two- and three-stage "W"-active regions that exhibit emission that is blue-shifted from the PL, due to charge separation and carrier band-filling of higher energy transitions. Further structure optimization, including multiple-stage (eight to ten W-stages) active regions is required to lower the threshold carrier density and minimize carrier band-filling and built-in electric field effects resulting from charge separation. Dilute nitride materials, such as GaAs1-y-zSbyNz/InP, are also under development offering potential for wavelength extension into the mid-IR employing InP substrates.