Growth and optical properties of InAs/GaAs quantum dot structures

Abstract

The growth and optical properties of InAs/GaAs(001) 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 2.7monolayers (ML) of InAs deposited at a rate of 0.25ML/s the dots have a dome shape and with increasing substrate temperature Ts from 460 to 520°C their surface density decreases from 2×1010 to 1.2×1010cm−2 and the mean lateral size increases from 40 to 70nm, the dots height does not exceed 8nm. At low beam equivalent pressure of As (below 3×10−6Torr) and higher Ts the segregation of In occurs. The multiple stacked QD structures (2.7 or 4ML of InAs with 4ML GaAs spacer) with the more uniform morphology in the upper layers providing the intense and narrow PL spectrum are formed at Ts=490°C and the flux ratio As4/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.