Improved 1.5 μm wavelength lasers using high quality LP-OMVPE grown strained-layer InGaAs quantum wells

Abstract

Strained-layer (SL) In x Ga 1− x As/ InP and In x Ga 1− x As/ InGaAsP QWs with 1.8% biaxial compressive strain have been grown by low pressure organometallic vapour phase epitaxy on 0.2° and 2° misoriented (001) InP substrates in the same growth run. The SL QWs grown on 2° misoriented substrates showed broad photoluminescence lines due to well width variations of about a factor of 2 resulting from 3D-like growth as revealed in TEM, whereas the corresponding SL QWs grown on 0.2° misoriented substrates showed narrow multiple line photoluminescence emissions. These multiple lines are ascribed to (half)-monolayer well width variations within one QW with atomically flat interfaces over areas larger than the excitonic diameter. SL-modulation-doped In x Ga 1− x As/ InGaAsP QWs were used to manufacture 1.5 μm wavelength DCPBH laser diodes. For the first time, significantly improved device characteristics were obtained. A differential external efficiency as high as 82%, a characteristic temperature as high as 97 K and CW output powers as high as 200 mW were measured. The improved device performances are ascribed to the strain-induced reduction of non-radiative recombination in the structures. Lifetests performed at 60°C heat-sink temperature and a CW output power of 5 mW showed almost no degradation after 4000 h.