Substrate orientation effect on potential fluctuations in multiquantum wells of GaAs/AIGaAs

摘要

The photoluminescence (PL) technique as a function of temperature and excitation intensity was used to study the optical properties of multiquantum wells (MQWs) of GaAs/ Al_x-Ga_(1-x)As grown by molecular beam epitaxy on GaAs substrates oriented in the [100], [311]A, and [311]B directions. The asymmetry presented by the PL spectra of the MQWs with an apparent exponential tail in the lower-energy side and the unusual behavior of the PL peak energy versus temperature (blueshift) at low temperatures are explained by the exciton localization in the confinement potential fluctuations of the heterostructures. The PL peak energy dependence with temperature was fitted by the expression proposed by Passler [Phys. Status Solidi B 200, 155 (1997)] by subtracting the term σ_E~2/k_BT, which considers the presence of potential fluctuations. It can be verified from the PL line shape, the full width at half maximum of PL spectra, the σ_E values obtained from the adjustment of experimental points, and the blueshift maximum values that the samples grown in the [311]A/B directions have higher potential fluctuation amplitude than the sample grown in the [100] direction. This indicates a higher degree of the superficial corrugations for the MQWs grown in the [311] direction.