Influence of bismuth doping of InAs quantum-dot layer on the morphology and photoelectronic properties of Gas/InAs heterostructures grown by metal-organic chemical vapor deposition

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Abstract
GaAs/InAs quantum dot (QD) heterostructures prepared by metalloorganic chemical vapor deposition (MOCVD) are investigated. It is established that the introduction of isovalent bismuth doping during the growth of InAs QD layer results in the suppression of the nanocluster coalescence and favors the formation of more uniform QDs. Bismuth itself is virtually not incorporated into the dots, its role being mainly in limiting the migration mobility of atoms at the surface of the growing layer. A method for investigating the morphology of buried layers of InAs QDs in GaAs matrix by atomic-force microscopy is developed; it relies on the removal of the cap layer by selective chemical etching. The photoluminescence (PL) and photoelectric sensitivity spectra of the fabricated heterostructures and their relation to the morphology of the QD layer are studied. In doped structures, PL and selective photosensitivity owing to the QDs are observed at a wavelength of 1.41 µm with the linewidth of 43 meV at room temperature. Some of the morphological features and photoelectronic properties of the MOCVD-grown heterostructures are related to the formation of a transitional layer at the GaAs/InAs QD interface due to the diffusion-induced mixing of the components.

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