In-situ position-controlled lateral deposition of nanometer-size Zn and Al dots on a sapphire substrate was accomplished by dissociating diethylzinc and trimethylaluminum using an optical near field on a sharpened optical fiber probe tip. The minimum diameters of the Zn and Al dots deposited were 37 and 25 nm, respectively, comparable with the apex diameter of the fiber probe. By changing the reactant molecules during deposition, nanometric Zn and Al dots were successively deposited on the same sapphire substrate with high precision. The distance between these dots was as short as 100 nm.

Optical properties and growth of self-assembled quantum dots (SAQDs) for optoelectronic device applications are discussed. After briefly reviewing the history of research on QD lasers, we discuss growth of InAs SAQDs including the light emission at the wavelength of 1.52-µm with a narrow linewidth (22 meV) and the area-controlled growth which demonstrates formation of SAQDs in selected local areas on a growth plane using a SiO2 mask with MOCVD growth. Then properties of the InGaAs AQDs are investigated by the near-field photoluminescence excitation spectroscopy which reveals gradually increasing continuum absorption connected with the two-dimensional-like (2D-like) wetting layer, resulting in faster relaxation of electrons due to a crossover between 0D and 2D character in the density of states. In the coherent excitation spectroscopy, the decoherence time is determined to be about 15 ps, which is well explained by the phonon induced relaxation mechanism in the SAQDs. Finally, nitride-based SAQDs and perspective of QD optical devices are also discussed.