Wavelength-tunable (1.55-μm region) InAs quantum dots in InGaAsP∕InP (100) grown by metal-organic vapor-phase epitaxy

Growth of wavelength-tunable InAs quantum dots (QDs) embedded in a lattice-matched InGaAsP matrix on InP (100) substrates by metal-organic vapor-phase epitaxy is demonstrated. As∕P exchange plays an important role in determining QD size and emission wavelength. The As∕P exchange reaction is suppressed by decreasing the QD growth temperature and the V∕III flow ratio, reducing the QD size and emission wavelength. The As∕P exchange reaction and QD emission wavelength are then reproducibly controlled by the thickness of an ultrathin [zero to two monolayers (MLs)] GaAs interlayer underneath the QDs. An extended interruption after GaAs interlayer growth is essential to obtain well-defined InAs QDs. Submonolayer GaAs coverages result in a shape transition from QD to quantum dash at low V∕III flow ratio with a slightly shorter emission wavelength. Only the combination of reduced growth temperature and V∕III flow ratio with the insertion of GaAs interlayers above ML thicknesses allows wavelength tuning of QDs at room temperature in the technologically important 1.55-μm wavelength region for fiber-optical telecommunication systems. A GaAs interlayer thickness just above one ML produces the highest photoluminescence (PL) efficiency. Temperature-dependent PL measurements reveal zero-dimensional carrier confinement and defect-free InAs QDs.