Luminescence properties of GaAs-Ga1−x Alx As double heterostructures and multiquantum-well superlattices grown by molecular beam epitaxy

Undoped double-heterostructures (DH) and multiquantum-well structures (MQW) grown by molecular beam epitaxy are studied by cathodoluminescence and photoluminescence. Their structural properties are established by scanning transmission electron microscopy. In DH discrete nonradiative centers are observed with densities ∼104–105 cm−2; some of them are correlated with dislocations originating in the substrate. In sharp contrast, MQW show a very uniform luminescence with no nonradiative action at dislocations. These results might explain in part the higher quantum efficiency of MQW grown by molecular beam epitaxy.