A detailed investigation on the impact of variation in growth rate, monolayer coverage and barrier thickness on the optical characteristics of InAs/GaAs bilayer quantum dot heterostructures

Abstract

We examined self-organized InAs/GaAs bilayer quantum dot (BQD) structures grown by solid source molecular beam epitaxy. The two layers had an intermediate GaAs barrier/spacer layer (SL) varying between 75Å and 200Å thicknesses. The photoluminescence (PL) characteristics of the InAs/GaAs BQDs were investigated by varying three growth parameters: (i) growth rate (monolayers per second, ML/s) of active dot layer, (ii) deposition amount (ML) of InAs on active dot layer while keeping that on the seed layer constant, and (iii) GaAs SL thickness (Ǻ). Analysis of temperature-dependent PL data indicated an optimum SL thickness of ∼100Å, for which the low-temperature PL emission peak is at ∼1.3μm with a full width at half-maximum of ∼24.5meV. BQD optimization was achieved with a slow (∼0.03ML/s) rather than fast (∼0.3ML/s) growth rate, and with a larger (3.2ML) rather than smaller (2.5ML) deposition of InAs on the active dot layer.