K. M. Gambaryan

Strain-induced InAsSbP islands and quantum dots grown by liquid phase epitaxy on a InAs(1?0?0) substrate

The liquid phase epitaxy technique is used for self-assembled InAsSbP-based strain-induced islands and quantum dots (QD) formation on InAs(1 0 0) substrates. The morphology, dimensions (size and shape), distribution density and composition of these objects are investigated by scanning electron and atomic force microscopies (SEM and AFM) and found to be self-organized from pyramids to globes. In addition, we perform energy dispersive x-rays analysis measurements at the top and bottom angles of the InAsSbP quaternary pyramids and lattice mismatch ratio calculations. They show that the strength at the top of the pyramids is lower than at the bottom angles, and that the island size becomes smaller when the lattice mismatch decreases. The QD average density ranges from 5 to 7 × 109 cm−2, with height and width dimensions from 0.7 nm to 25 nm and 20 nm to 80 nm, respectively. A critical size (~500 nm) for the transformation of the InAsSbP-based strain-induced pyramid shape to globe shape is determined.

Interaction and Cooperative Nucleation of InAsSbP Quantum Dots and Pits on InAs(100) Substrate

An example of InAsSbP quaternary quantum dots (QDs), pits and dots–pits cooperative structures’ growth on InAs(100) substrates by liquid phase epitaxy (LPE) is reported. The interaction and surface morphology of the dots–pits combinations are investigated by the high-resolution scanning electron microscope. Bimodal growth mechanism for the both QDs and pits nucleation is observed. Cooperative structures consist of the QDs banded by pits, as well as the “large” pits banded by the quantum wires are detected. The composition of the islands and the pits edges is found to be quaternary, enriched by antimony and phosphorus, respectively. This repartition is caused by dissociation of the wetting layer, followed by migration (surface diffusion) of the Sb and P atoms in opposite directions. The “small” QDs average density ranges from 0.8 to 2 × 109 cm−2, with heights and widths dimensions from 2 to 20 nm and 5 to 45 nm, respectively. The average density of the “small” pits is equal to (6–10) × 109 cm−2 with dimensions of 5–40 nm in width and depth. Lifshits–Slezov-like distribution for the amount and surface density of both “small” QDs and pits versus their average diameter is experimentally detected. A displacement of the absorption edge toward the long wavelength region and enlargement toward the short wavelength region is detected by the Fourier transform infrared spectrometry.

Room temperature magnetoelectric properties of type-II InAsSbP quantum dots and nanorings

Quaternary InAsSbP quantum dots (QDs) and quantum rings (QRs) are grown on InAs (100) substrates by liquid phase epitaxy. High resolution scanning electron and atomic force microscopes are used for the characterization. The room temperature optoelectronic and magnetoelectric properties of the InAsSbP type-II QDs and QRs are investigated. For the QD-based structures, specific dips on the capacitance-voltage characteristic are revealed and measured, which are qualitatively explained by the holes thermal and tunnel emissions from the QDs. Specific fractures at room temperature are experimentally found in the magnetic field dependence of an electric sheet resistance for the InAsSbP QRs-based sample.

Growth process, characterization, and modeling of electronic properties of coupled InAsSbP nanostructures

Quaternary III-V InAsSbP quantum dots (QDs) have been grown in the form of cooperative InAsSb/InAsP structures using a modified version of the liquid phase epitaxy. High resolution scanning electron microscopy, atomic force microscopy, and Fourier-transform infrared spectrometry were used to investigate these so-called nano-camomiles, mainly consisting of a central InAsSb QD surrounded by six InAsP-QDs, that shall be referred to as leaves in the following. The observed QDs average density ranges from 0.8 to 2 × 109 cm-2, with heights and widths dimensions from 2 to 20 nm and 5 to 45 nm, respectively. The average density of the leaves is equal to (6-10) × 109 cm-2 with dimensions of approx. 5 to 40 nm in width and depth. To achieve a first basic understanding of the electronic properties, we have modeled these novel nanostructures using second-order continuum elasticity theory and an eight-band k·p model to calculate the electronic structure. Our calculations found a clear localization of hole states in th...

The Ostwald ripening at nanoengineering of InAsSbP spherical and ellipsoidal quantum dots on InAs (100) surface

We present the results of growth of quasi-ternary InAsSbP spherical and ellipsoidal quantum dots (QDs) on InAs (100) surface by the method of liquid-phase epitaxy. Coarsening of QDs due to coalescence and Ostwald ripening was investigated by atomic-force and scanning electron microscopy. Ellipsoidal QDs prolated in [010] and oblated in [001] directions have been grown. Elongation ratios for the ellipsoidal QDs were measured in all three directions. It is shown that elongation of spherical QDs to ellipsoidal is started at QDs diameter of ∼50 nm. Shape transformation of the QDs’ size distribution function from the Gram-Charlier-like to the Gaussian and then to the Lifshits-Slezov-like distribution was revealed at increasing the nucleation time.

Nucleation features and energy levels of type-II InAsSbP quantum dots grown on InAs(100) substrate

The nucleation features and measurements of holes energy levels of the InAsSbP type-II quantum dots (QDs) with respect to the InAs valence band edge by employing magnetospectroscopy and a photo- and electroluminescence measurements are reported. Three samples are prepared for investigations. The first and second samples consist of unencapsulated spherical and ellipsoidal QDs, respectively. Third sample is a n-InAs/p-InAsSbP heterostructure with QDs embedded into the p-n junction interface. The measured value for the holes first state is ∼33 meV above the InAs valence band. The hysteresis of 0.483 pF and contra-directional oscillations on the first sample’s capacitance-voltage characteristic is detected.

Silicon on glass grown from indium and tin solutions

A two-step process is used to grow crystalline silicon (c-Si) on glass at low temperatures. In the first step, nanocrystalline seed layers are formed at temperatures in the range of 230 to 400°C by either metal-induced crystallization or by direct deposition on heated substrates. In the second step, c-Si is grown on the seed layer by steady-state liquid phase epitaxy at a temperature range of 580 to 710°C. Microcrystalline Si layers with grain sizes of up to several tens of micrometers are grown from In and Sn solutions. Three-dimensional simulations of heat and convective flow in the crucible have been conducted and give valuable insights into the growth process. The experimental results are promising with regard to the designated use of the material in photovoltaics.

Narrow bandgap mid-infrared photodetectors based on InAsSbP quantum dots

The results of investigations of mid-infrared photodetectors based on InAsSbP quantum dot (QD) grown on InAs(100) substrate by modified liquid phase epitaxy are presented. The atomic force microscope measurements have shown that the surface density of grown QDs is (4–8) × 109 cm−2. Also, the morphology and crystalline quality of grown QDs are investigated by a scanning tunneling microscope. Photodetectors based on n-InAs(100) substrate with InAsSbP QDs on its surface were fabricated in the form of a photoconductor cell. The photoresponse spectrum extended up to 4 μm was observed. The optical properties of fabricated structures were investigated under He–Ne laser irradiation with wavelength of 1.15 μm. It was found that the relative surface conductance increases by 16% at power density of 0.15 W/cm2. Capacitance hysteresis with maximal remnant capacitance of 2.17 nF at 103 Hz was observed as well.

Investigation of photoelectrical properties of epitaxially grown heterojunction thermophotovoltaic cells

By the method of metal-organic chemical vapor deposition we have epitaxially grown effective samples of InAs/p-GaSb/n-GaSb/n-GaAs/InxGa1−xAs/Ge/Si(113) photovoltaic cells and investigated their photoelectric properties. The suitability of application of quality heterojunction diode structures in termophotovoltaic cells is experimentally proved.

The Growth of Low Band‐Gap InAsSbP Based Diode Heterostructures for Thermo‐Photovoltaic Application

This report describes our efforts to fabricate lattice matched p‐InAsSbP/n‐InAs and p‐InAsSbP/n‐InAsSbP/n‐InAs epitaxial diode heterostructures for TPV converter applications. A new version of liquid‐phase electroepitaxy, step — cooling LPE technique as well as MOVPE have been employed. The investigations of cross‐sectional area of p‐n heterojunctions, morphology of layers surface and calculations of quaternary InAsSbP alloys composition have been curried out using SEM‐EDX equipment. Epitaxial structures had a uniform thickness, a mirror‐like surface and a very flat interface. The I‐V characteristics, spectral response and other parameters of diode structures have been investigated. According to our previous results we believe that InAsSbP based devices are attractive for TPV application at low temperature (less than 1200K) emitters.