Growth and optical properties of InAs/GaAs quantum dot structures

The growth and optical properties of InAs/GaAs(0 0 1) quantum dot (QD) structures depending on the deposition parameters are investigated. The epitaxial layers were grown in a Riber 32P MBE system and studied by atomic force microscopy and photoluminescence (PL). For a single QD with 2.7 monolayers (ML) of InAs deposited at a rate of 0.25 ML/s the dots have a dome shape and with increasing substrate temperature Ts from 460 to 520 8C their surface density decreases from 2 1010 to 1:2 1010 cm 2 and the mean lateral size increases from 40 to 70 nm, the dots height does not exceed 8 nm. At low beam equivalent pressure of As (below 3 10 6 Torr) and higher Ts the segregation of In occurs. The multiple stacked QD structures (2.7 or 4 ML of InAs with 4 ML GaAs spacer) with the more uniform morphology in the upper layers providing the intense and narrow PL spectrum are formed at Ts ¼ 490 8C and the flux ratio As4/In ¼ 25. The high-quality modulated Si-doped InAs/GaAs QDs-based multilayer heterostructures N-AlGaAs/GaAs/InAs/GaAs/InAs/GaAs/ . . . /GaAs with the two-dimensional (2D) electron gas of high-density were grown and studied for the first time and in their low-temperature PL spectra the features associated with quantum confinement effects were observed. # 2003 Elsevier B.V. All rights reserved.