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Barrier composition dependence of the emission properties of AlGaInAs/GaInAs quantum wells grown by molecular beam epitaxy
The emission properties of (AlxGa1-x)0.48In0.52As/Ga0.47In0.53As quantum wells grown lattice-matched to InP substrates by molecular beam epitaxy have been systematically studied as a function of the Al content of the (AlxGa1-x)0.48In0.52As barrier material. Incorporating (AlxGa1-x)0.48In0.52As barrier material with low-temperature photoluminescence line widths, FWHM, approaching recently published record values, high-quality quantum wells were achieved. Taking into account a measured linear dependence of (AlxGa1-x)0.48In0.52As band gap on alloy composition, the calculated quantum well emission energies as a function of well width and barrier alloy composition are in close agreement with experimental values. The quantum well quality as judged from FWHM values revealed a systematic dependence on barrier composition. In contrast to an expected reduction of the FWHM values due to the narrowing of the involved energy levels with increasing barrier height the experimentally observedincreasing FWHM values coincide with the increasing amount of broadening due to alloy clustering in the barrier layers with Al content. This correspondence clearly demonstrates that the FWHM of the emission from (AlxGa1-x)0.48In0.52As/Ga0.47In0.53As quantum wells is limited by the optical quality of the (AlxGa1-x)0.48In0.52As barrier materials rather than by interface roughness of the heterointerfaces involved or by alloy broadening of the well material.