Molecular-beam epitaxy of metamorphic InAs/InGaAs quantum-dot heterostructures emitting in the telecom wavelength range

Heterostructures with InAs/InGaAs quantum dots grown by molecular beam epitaxy on the surface of InGaAs metamorphic buffer layers with a linearly graded composition profile on GaAs(001) substrates have been studied by X-ray diffraction, transmission electron microscopy, and, upon the growth of an additional quantum-dot layer on the surface of the structure, by atomic force microscopy. The tendency to the formation of quantum objects elongated along the [1–10] direction (so-called quantum dashes), caused by asymmetry in the surface migration of In along different crystallographic directions, is confirmed. It is established that the surface density of both quantum dots and quantum dashes is as high as $(2{-}4)\times 10^{10}$ cm$^2$. At the same time, narrow lines associated with emission from individual quantum dots are observed in the spectra of low-temperature ($T = 10$ K) microphotoluminescence in a wide wavelength range ($1.30$–$1.55$ $\mu$m). The size and shape of quantum dots have been estimated from atomic-force microscopy and transmission electron microscopy data and good agreement with the previously reported parameters is demonstrated.