Enhanced optical crystal quality of strain-compensated InGaAs/InGaAsP quantum-well structures on GaAs substrates by the introduction of intermediate-strain layers

To improve the crystal quality of heterointerfaces in InGaAs/InGaAsP strain-compensated quantum-well structures on (001) GaAs substrates, we added layers with intermediate levels of strain between the well and barriers. Photoluminescence measurements confirmed that the crystal quality of the heterointerfaces was improved by adding these intermediate layers. The greatest improvement was attained with an intermediate layer thickness of 4 monolayers and a strain at about the midpoint between that of QWs and barriers. The mean time to failure of fabricated 0.98-μm laser diodes (LDs) with such intermediate-strain layers was found to be about five times longer than that of LDs without the intermediate-strain layer