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[en] We present cantilever-probe based scanning near-field microscopy (SNOM) studies of GaInP microdisks resonators (radii R=2 um and quality factors Q∼1000) with embedded InP quantum dots (QDs) emitting at ∼750 nm. Near-field photoluminescence spectroscopy in collection regime, using side excitation from micro-objective, was used for imaging of whispering-gallery modes (WGMs) with a spatial resolution below the light diffraction limit. Using collection-illumination regime we imaged the position of single InP/GaInP QDs in microdisk. (paper)

[en] We used high spatial resolution near-field scanning optical microscopy (NSOM) to measure low-temperature (10K) emission spectra of single InP/GaInP QDs (lateral size ∼100 nm) at magnetic fields up to 10 T. A multi-electronic structure having energy splitting 3-5 meV, resulting from charging of the dot up to 20 electrons, has been observed for these QDs. We measured a strong variation of the near-field emission intensity on a length scale ∼30 nm related to Wigner localization. Magnetic-field-induced shifts of the multi-shell peaks for some dots follow remarkably well the energy levels of a Fock-Darwin Hamiltonian, which allow the observation of a Wigner-molecular-droplet transition.

[en] We used a low temperature near-field scanning optical microscopy (NSOM) to study a formation of Wigner molecules (WMs) in the emission spectra of self-organized InP/GaInP QDs having up to seven electrons. We used a Schottky diode structure for the electrostatic control of the number of the electrons (N) in QD, and we observed the emission of the charged excitons (for N < 3) and of the WMs (for N > 2) in the regime of weak Wigner localization. We show, that a contribution of whispering gallery modes (WGMs) of the electrons and rearrangement of the electrons between the WM and WGM states in the QDs, can explain the anomalous dependence of NSOM image size on the quantum confinement observed for some dots.

[en] The MOVPE growth of InP/GaInP quantum dots (QDs) on GaAs substrate “defects” formed by a focused beam of Ga"+ ions is studied. It is shown that ordered arrays of QDs with a density of 0.25 (μm)"−"2 can be obtained in the InP/GaInP system. It is demonstrated that effective luminescence can be obtained by using two QD sheets separated by a GaAs/GaInP buffer layer

[en] Properties of light-emitting structures with an InGaN/GaN active region emitting in a range of 500-550 nm are studied. Photoluminescence of the structures is studied at various values of external bias and temperature as well as with time resolution. With the reverse bias, a decrease in the carrier lifetime associated with tunneling exit of the carriers from the active region is found. The mechanism of tunneling leakage is simulated allowing for the Boltzmann distribution of carriers by energy; it is shown that the calculated and experimental dependences agree well. It is shown that the tunneling transport exerts a considerable effect on the characteristics of structures with an InGaN/GaN active region.

[en] Microphotoluminescence (μPL) spectra of single In(Ga)P/GaInP quantum dots (QD) were investigated. Measurements were carried out at different optical pump power and at different electric field with constant optical pump. Filling of electron s-, p-, d-states was observed. Quantum confinement Stark effect (QCSE) was detected. Obtained PL life times of s-, p- electron states were 0.5 ns and 0.4 ns respectively. From spectra it is clearly seen that QDs have weak quantum confinement (hω₀∼4-8meV). (paper)

[en] This work presents the results of the growth, structural characterization and magneto-photoluminescence spectroscopy measurements of GaAs/AlGaAs/InP/GaInP₂ quantum well-quantum dot structures. We demonstrate that GaAs/AlGaAs QDs in these structures are formed above InP/GaInP₂ QDs. This allows us to measure the internal magnetic field in the InP/GaInP₂ QD by monitoring the Zeeman splitting of the excitonic transition in the GaAs/AlGaAs QD. (paper)

[en] AlInAs microdisk cavities having quality factor Q ∼ 15 000 were fabricated from lattice-matched InP/AlInAs (interface/aggregation) quantum dot (QD) structures using wet chemical etching. The QD emission coupled to whispering gallery modes was observed at spectral range 920 - 1000 nm at temperatures of 10 - 160 K. The laser generation with threshold power density of 50 W/cm"2 at T = 10 K was observed under optical pumping. It was found that the spontaneous emission coupling factor β equals 0.23 for these microdisks. The low temperature lasing operation and the small coupling factors observed suggest the existence of small QDs formed at the InP/InAlAs interface as the main active elements. (paper)

[en] Near-field scanning optical microscopy (NSOM) with a spatial resolution below the light diffraction limit was used to study intensity distributions of the whispering gallery modes (WGMs) in quantum dot-based microdisk and microring lasers on GaAs with different outer diameters. Room temperature microphotoluminescence study (μPL) reveal lasing in microlasers of both geometries. (paper)