Ya. A. Parkhomenko

InSb/InAs quantum dots grown by liquid phase epitaxy

The first original results on the growth of quantum dots (QDs) in the InSb/InAs system by liquid phase epitaxy (LPE) are reported. The density and dimensions of QDs were studied by methods of scanning probe microscopy and atomic force microscopy. The surface density, shapes, and dimensions of LPE-grown nanoislands depend on the growth conditions (temperature, cooling rate, and solution melt-substrate contact time). In the interval of temperatures T = 420–445°C, homogeneous arrays of InSb quantum dots on InAs(100) substrates were obtained with an average height of H = 3.4 ± 1nm, a radius of R = 27.2 ± 7.5 nm, and a density of up to 1.9 × 1010 cm−2.

Specific features of the epitaxial growth of narrow-gap InSb quantum dots on an InAs substrate

Arrays of coherent InSb quantum dots (QDs) have been fabricated by liquid-phase epitaxy on InAs substrates in the temperature range T = 420–450°C. The QDs with a density of (0.9−2) × 1010 cm−2 were 3 nm high and 13 nm in diameter. A bimodal QD size distribution was observed, which was accounted for by a combined growth mechanism of these nanoobjects. Structural characteristics of a separate InSb QD formed on the InAs surface were studied for the first time by atomic-force and transmission electron microscopies. Moire fringes were observed for the first time for QDs in the InSb/InAs system, with the moire period of 3.5 nm corresponding to InSb QDs without an admixture of arsenic.

Type II heterostructures with InSb quantum dots inserted into p-n InAs(Sb,P) junction

We report on study of electrical and optical properties of type II heterostructures with InSb quantum dots (QDs) inserter into the InAs-based p-n junction made by LPE-MOVPE combine method. InSb QDs were grown on an InAs(100) substrate by LPE. Overgrowth on the surface with the self-assembled InSb QD arrays was performed by MOVPE using capping layers based on binary InAs and quaternary InAsSb solid solutions. High-resolution cross-sectional image of the InSb QDs buried into the InAs(Sb,P) matrix was obtained for the first time by transmission electron microscopy. Structural parameters of the InSb QDs such as size, shape and internal strain were demonstrated and discussed. The uniform small QDs with high density (>1010 cm-2) with dimensions of 3 nm in height and 14 nm in diameter were found to be self-assembled and dislocation-free without any extended defects, whereas the low-density large QDs (108 cm-2) with dimensions of 10 nm in height and 50 nm in diameter were relaxed and demonstrated interface strain with the InAs substrate. I-V characteristics of the mesa-diode heterostructures with the InSb QDs inserted into InAs p-n junction were studied at the wide temperature range T=77-300 K. Intense positive and negative electroluminescence for both n-InAs/p- InAs and n-InAs/InSb-QDs/p-InAs heterostructures was found in the spectral range 3-4 μm. Evolution of the spectra in dependence on applied external bias (forward and reverse) were observed at 77 K and 300 K.

InSb quantum dots and quantum rings in a narrow-gap InAsSbP matrix

We report a study of InSb quantum dots and quantum rings grown on InAs(100) substrate by LPE-MOVPE combine method. Characterization of InSb/InAs(Sb,P) quantum dots was performed using atomic force microscopy and transmission electron microscopy. The bimodal growth of uncapped InSb quantum dots was observed in the temperature range T=420-450 °C. The low-density (5×108 cm-2) large quantum dots with dimensions of 12-14 nm in height and 45-50 nm in diameter are appeared at 445 °C, whereas high-density (1×1010 cm-2) dislocation-free small quantum dots with dimensions of 3-5 nm in height and 11-13 nm in diameter were obtained at 430 °C. Capping of the InSb quantum dots by binary InAs or InAsSbP epilayers lattice-matched with InAs substrate was performed using MOVPE method. Tunnel-related behavior in a forward curve of I-V characteristics was observed in heterostructures with buried InSb quantum dots inserted in InAs p-n junction. Evolution of electroluminescence spectra on driving current at negative bias and suppression of negative luminescence from buried InSb/InAs quantum dots were found out in the spectral range 3-4 μm at 300 K. Deposition from the InSb melt over the InAsSb0.05P0.10 capping layer resulted in the formation of InSb quantum rings with outer and inner diameters about 20-30 nm and 15-18 nm respectively. Surface density of the quantum rings of 2.6×1010 cm-2 was reached at 430 °C.

Influence of tellurium impurity on the Properties of Ga1−XInXAsYSb1−Y (X>0.22) solid solutions

The influence of tellurium impurity on the electrical properties of Ga1−XInXAsYSb1−Y (X=0.22 and X=0.24) solid solutions grown by liquid-phase epitaxy from lead-containing solution-melts was studied. Defect healing was shown to take place at low tellurium doping levels (XTeL<2×10−5 at. %) in inhomogeneous highly compensated p-type solid solutions. Thus, it is possible to produce slightly compensated p-type materials with a low density of impurities and structural defects. High doping levels allow production of n-type materials with the electron density n=1017–1019 cm−3. Electroluminescence spectra of n-GaInAsSb/p-GaSb heterostructures are promising for the development of light-emitting diodes with a wavelength λ=2.0–2.5 µm.

Quantum dots grown in the InSb/GaSb system by liquid-phase epitaxy

The first results of the liquid-phase epitaxial growth of quantum dots in the InSb/GaSb system and atomic-force microscopy data on the structural characteristics of the quantum dots are reported. It is shown that the surface density, shape, and size of nanoislands depend on the deposition temperature and the chemical properties of the matrix surface. Arrays of InSb quantum dots on GaSb (001) substrates are produced in the temperature range T = 450–465°C. The average dimensions of the quantum dots correspond to a height of h = 3 nm and a base dimension of D = 30 nm; the surface density is 3 × 109 cm–2.

InSb quantum dots produced by liquid-phase epitaxy on InGaAsSb/GaSb substrates

Indium-antimonide quantum dots are for the first time formed on the surface of an epitaxial In0.25GaAsSb layer isoperiodic to a GaSb(001) substrate by liquid-phase epitaxy in the range of temperatures T = 450–467°C. Transmission electron microscopy shows that, the shape of quantum dots is close to a truncated cone and their distribution in terms of height and base size in the ensemble is monomodal. Large-sized quantum dots (with a base size of 30–50 nm and height of 3 nm) exhibit specific contrast in the plane-view diffraction-mode image, which is indicative of the presence of misfit defects. Modification of the chemical composition of the working surface of the substrate by the deposition of an epitaxial In0.25GaAsSb layer makes possible a threefold increase in the density of the ensemble of InSb quantum dots (1 × 1010 cm–2) compared to the density in the case of deposition directly onto the GaSb binary compound.

Specific features of electroluminescence in heterostructures with InSb quantum dots in an InAs matrix

The electrical and electroluminescence properties of a single narrow-gap heterostructure based on a p-n junction in indium arsenide, containing a single layer of InSb quantum dots in the InAs matrix, are studied. The presence of quantum dots has a significant effect on the shape of the reverse branch of the current-voltage characteristic of the heterostructure. Under reverse bias, the room-temperature electroluminescence spectra of the heterostructure with quantum dots, in addition to a negative-luminescence band with a maximum at the wavelength λ = 3.5 μm, contained a positive-luminescence emission band at 3.8 μm, caused by radiative transitions involving localized states of quantum dots at the type-II InSb/InAs heterointerface.

The effect of tellurium diffusion from an n-GaSb:Te substrate on the properties of GaInAsSb solid solutions grown from lead-containing melt

The effect of tellurium diffusion from an n-GaSb:Te substrate on the transport and photoelectric properties of GaInAsSb solid solutions grown from lead-containing melt is investigated. The strongest influence observed for tellurium diffusion from the substrate is in 1-to 2-μm-thick epitaxial layers of solid solutions with low hole density and hole mobility. Under the illumination of these samples, a large photovoltage is observed in the spectral range of band-gap absorption.

The role of lead in growing Ga1−XInXAsYSb1−Y solid solutions by liquid-phase epitaxy

The electrical properties of Ga1−XInXAsYSb1−Y (X=0.14–0.27) solid solutions grown from a Pb-containing solution-melt were investigated for the first time. Three acceptor levels were found to exist, specifically, a shallow level with the activation energy EA1≈0.008–0.015 eV, and two deep levels EA2≈0.024–0.033 eV and EA3≈0.07 eV. It is demonstrated that the use of Pb makes it possible to obtain undoped solid solutions with a low concentration of defects and impurities and with high carrier mobility.