Carrier diffusion on atomically flat (1 1 0) GaAs quantum wells

By means of cleaved-edge overgrowth method with molecular beam epitaxy and growth interrupt annealing, we fabricated (110) GaAs quantum wells having atomically flat interfaces. We introduced characteristic 1-Monolayer(ML)-deep pits and 2–3-ML-high islands on atomically flat interfaces by adding fractional monolayer of GaAs, which are characterized by atomic force microscope. In Photoluminescence(PL) observation with uniform excitation, pits are reproduced as dark triangle images due to higher energy than surroundings, and islands as bright PL spots due to lower energy. With increasing temperature, we observe changes in their shape and enhanced contrast, which are explained by enhanced carrier diffusion length due to significant reduction of interface-roughness scattering.