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

The Photoreflectance (PR) technique was applied to evaluate a 25-period Al0 .27Ga0.73As/GaAs multiquantum-well (MQW) structure with a well length of 55 Angstrom grown by atmospheric pressure metalorganic vapor phase expitaxy ( MOVPE) on a (111)A GaAs substrate. Structural parameters such as well and b arrier lengths, and the Al fraction in the barriers were accurately determi ned by high resolution X-ray diffractometry (HRXRD). The PR spectrum exhibi ts all the possible confined QW transitions between electron and hole sub-b ands. The theoretically calculated transition energies are in very close ag reement(+/-1 meV) with those experimentally determined from the PR spectrum even up to the highest possible transition for these wells. From a detaile d monolayer (ML) analysis of the various transition energies it is conclude d 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 addi tion, 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-peri od MQW in agreement with the PR analysis. This FWHM is the best value repor ted to date for AlGaAs/GaAs MQW structures grown on {111} GaAs substrates e ither by MBE or MOVPE. (C) 1999 Elsevier Science S.A. All rights reserved.