Effect of periodic interruption of the atmospheric-pressure MOVPE growth of InAs/GaAs quantum dots on their morphology and optoelectronic spectra

A modified regime of growing InAs/GaAs quantum dots (QDs) by metalorganic vapor phase epitaxy (MOVPE) at atmospheric pressure is described. In contrast to the standard growth regime, the time of periodic interruption of the supply of trimethylindium and arsin to the reactor was increased and varied from 4 to 18 s. It is shown that optimization of the interruption time leads to the formation of dense, homogeneous (with respect to dimensions) QD arrays and to a decrease in the concentration of coarse relaxed clusters without using additional treatments (e.g., doping with surfactants, chemical etching). In particular, the surface concentration of QDs increases up to 6 × 10¹⁰ cm⁻², that is, by almost an order of magnitude as compared to the standard growth regime. QD structures grown using the modified MOVPE method are characterized by high thermal stability and ensure high intensity of room-temperature electroluminescence of the related edge-emitting Schottky diodes.     

Study of the Transport Properties and Domain Structure of Thin CoPt Films Obtained by Electron Evaporation

Journal of Communications Technology and Electronics - Abstract—CoPt films obtained by electron beam evaporation with deposition of ten Co and Pt bilayers with a total thickness of 8 nm are...     

Circularly Polarized Electroluminescence of Spin LEDs with a Ferromagnetic (In,Fe)Sb Injector

Technical Physics Letters - The possibility of using a diluted magnetic semiconductor (In, Fe)Sb as a functional layer for use in spintronics, namely, as a ferromagnetic injector in a spin light...     

Optoelectronic properties of heteronanostructures with combined layers of In(Ga)As/GaAs quantum wells and dots

The effect of the incorporation of an InGaAs quantum well into structures with InAs/GaAs quantum dots grown by gas-phase epitaxy on their optoelectronic properties is analyzed in the mode with increased growth-interruption time. It is established that the quantum-dot energy spectrum is weakly sensitive to variations in the thickness and composition of the double InGaAs/GaAs coating layer. The deposition of a quantum well onto a layer of quantum dots decreases the emission-barrier effective height in them. The conditions under which the quantum well can be used for protecting the quantum-dot active layer against penetration by defects generated during structure-surface anodic oxidation are determined.     

On the crystal structure and thermoelectric properties of thin Si<Subscript>1–<Emphasis Type="Italic">x</Emphasis> </Subscript>Mn<Subscript> <Emphasis Type="Italic">x</Emphasis> </Subscript> films

Thin (25 nm) Si_1–xMn_x/Si(100) films are fabricated by pulsed laser deposition. According to high-resolution transmission electron microscopy data, the films have a nanotextured crystalline structure and are chemically homogeneous. The temperature dependences of the resistivity and thermopower are measured in the range of 300–500 K, and the temperature dependences of the Seebeck coefficient and power factor are calculated.     

Diagnostics of the efficiency of surface plasmon-polariton excitation by quantum dots via polarization measurements of the output radiation

It is demonstrated that the efficiency of surface plasmon-polariton excitation at a metal-semiconductor interface by active quantum dots can be determined from measurements of the polarization characteristics of the output radiation. Experimentally, the proposed diagnostic method is based on finding the ratio of the intensities of the output radiation with polarizations orthogonal and parallel to the nanoheterostructure plane for two different distances between the quantum-dot layer and the metal-semiconductor interface. These data are then used to obtain the unknown parameters in the proposed mathematical model which makes it possible to calculate the rate of surface plasmon-polariton excitation by active quantum dots. As a result, this rate can be determined without complicated expensive equipment for fast time-resolved measurements.

     

Effect of the electrochemical modification of a thin Ga(In)As cap layer on the energy spectrum of InAs/GaAs quantum dots

It was shown that the selective etching and anodic oxidation of a thin Ga(In)As cap layer makes it possible to decrease the ground-state transition energy in InAs/GaAs quantum dots from ～0.9 to ～0.7 eV due to the resulting partial stress relaxation. Similar processing of surface quantum dots leads to a decrease in the quantum-dot height that increases the transition energy.     

The effect of ferromagnetic Mn-delta-doped layer on the emission properties of GaAsSb/GaAs and InGaAs/GaAsSb/GaAs heterostructures

We have studied the emission characteristics and circularly polarized electroluminescence of light-emitting diodes based on heterostructures with a single (GaAs/GaAsSb/GaAs) or two-layer (GaAs/InGaAs/GaAsSb/GaAs) quantum well (QW) and a Mn-delta-doped layer in the GaAs barrier. The ferromagnetic effect of the delta-layer of Mn on the spin polarization of carriers in QWs based on type-II heterostructures has been observed and studied for the first time. The observed phenomena are described using a model of the exchange interaction of Mn ions in the barrier and holes in the QW.     

Diode Structures Based on (In,Fe)Sb/GaAs Magnetic Heterojunctions

Technical Physics Letters - The current–voltage characteristics of light-emitting diodes based on InGaAs/GaAs heterostructures with an injector made of (In, Fe)Sb diluted magnetic...     

Specific features of photoluminescence of InAs/GaAs QD structures at different pumping levels

Photoluminescence spectra of InAs/GaAs QD structures have been studied at different pumping powers and temperatures. At low pumping levels, one of the spectral lines in an undoped sample is shifted as the power increases. As the temperature increases, the luminescence intensity in the high-energy portion of the spectrum decreases, and the low-energy spectrum is red-shifted. The presence of QDs of two characteristic sizes is demonstrated.