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 T s from 460 to 520 °C their surface density decreases from 2×10 10 to 1.2×10 10 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 T s 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 T s =490 °C and the flux ratio As 4 /In=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.