GaAs cap layer growth and In-segregation effects on self-assembled InAs quantum dots monitored by optical techniques

The overgrowth of InAs islands by a GaAs cap layer has been investigated by optical in situ measurements at various growth conditions. A better smooth ing of the surface has been found for low growth rates. This effect is attr ibuted to a larger diffusion length of the gallium during growth leading to a smoother final surface. The status of the surface during and after cap l ayer growth can be determined from RAS and SE measurements during growth. T his correlation between the optical data and the surface morphology was con firmed by ex situ AFM measurements. Post growth annealing of samples with d ifferent cap layer thickness showed indium interdiffusion from the islands to the cap layer over several nanometers. This effect is also observed duri ng cap layer growth at higher temperatures and can be attributed to indium segregation during growth. (C) 1998 Elsevier Science B.V. All rights reserv ed.