Photoreflectance evaluation of MOVPE AlGaAs/GaAs multiple quantum wells on (111)A GaAs

Abstract The Photoreflectance (PR) technique was applied to evaluate a 25-period Al 0.27 Ga 0.73 As/GaAs multiquantum-well (MQW) structure with a well length of 55 A grown by atmospheric pressure metalorganic vapor phase expitaxy (MOVPE) on a (111)A GaAs substrate. Structural parameters such as well and barrier lengths, and the Al fraction in the barriers were accurately determined by high resolution X-ray diffractometry (HRXRD). The PR spectrum exhibits all the possible confined QW transitions between electron and hole sub-bands. The theoretically calculated transition energies are in very close agreement (±1 meV) with those experimentally determined from the PR spectrum even up to the highest possible transition for these wells. From a detailed monolayer (ML) analysis of the various transition energies it is concluded that the QW interfaces have much less than a ±1 ML fluctuation over the 25 periods and that the interfaces are smooth, abrupt and uniform. In addition, photoluminescence (PL) measurements were also used to further assess the optical quality. The PL full width at half maximum (FWHM) is 12.5 meV, which corresponds to less than a ±1 ML fluctuation throughout the 25-period MQW in agreement with the PR analysis. This FWHM is the best value reported to date for AlGaAs/GaAs MQW structures grown on {111} GaAs substrates either by MBE or MOVPE.