Engineering topics

Aleshkin, V. Ya.

Publications and source records attributed to Aleshkin, V. Ya..

At least 19 records

DOE OSTI2019

Study of the Auger Recombination Energy Threshold in a Series of Waveguide Heterostructures with HgTe/Cd{sub 0.7}Hg{sub 0.3}Te QWs Near 14 μm

Stimulated emission from a heterostructure with Hg{sub 0.903}Cd{sub 0.097}Te/Cd{sub 0.7}Hg{sub 0.3}Te quantum wells, placed in a waveguide layer of wide-gap CdHgTe, is obtained at wavelengths of 14–11 μm and a temperatures of 18–80 K. The threshold Auger recombination energy is calculated for a set of heterostructures with quantum wells of pure HgTe with a band gap of 90 meV (wavelength 14 μm). The possibility of fabricating lasers operating at 14 μm and working temperatures higher than that of liquid nitrogen is demonstrated.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2019

Submonolayer InGaAs/GaAs Quantum Dots Grown by MOCVD

The mode of the growth of InGaAs quantum dots by MOS-hydride epitaxy on GaAs substrates without a deviation and with a deviation of 2° is selected for laser structures emitting at wavelengths above 1.2 μm at room temperature. As a result, a quantum-dot density of 4 × 10{sup 10} cm{sup –2} is achieved. Stimulated emission is observed in laser structures with seven layers of quantum dots at a wavelength of 1.06 μm at liquid-nitrogen temperature. The threshold power density of optical pumping is about 5 kW/cm{sup 2}.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2019

Generation of THz radiation at a difference frequency in a HgCdTe-based laser

The results of a theoretical study of THz radiation generation at a difference frequency in a HgTe/HgCdTe quantum-well laser are presented. It is shown that in such a laser having a waveguide width of 100 μm, at the power 1 W of the near-IR radiation modes the radiation power at the difference frequency in the range 0.5 – 3.5 THz reaches 90 μW at room temperature. (terahertz radiation)

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2019

Effect of Cd content in barriers on the threshold energy of Auger recombination in waveguide structures with HgTe/Cd{sub x}Hg{sub 1 – x}Te quantum wells, emitting at a wavelength of 18 μm

The threshold energy of Auger recombination in HgTe/Cd{sub x}Hg{sub 1 – x}Te heterostructures with quantum wells (QWs) is analysed numerically for different compositions of the solid solution in barriers. It is demonstrated that the threshold energy depends nonmonotonically on the cadmium content in barriers and reaches a maximum at x ∼0.6 – 0.7. A comparison of the results of numerical calculations with experimental data on the temperature quenching of stimulated emission in a Cd{sub 0.1}Hg{sub 0.9}Te/Cd{sub 0.65}Hg{sub 0.35}Te structure gives grounds to expect a more than twofold increase in the quenching temperature of stimulated emission in structures with pure HgTe QWs and barriers with a high (∼0.6) cadmium content. (paper)

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2018

Photodetectors with an InGaAs Active Region and InGaP Metamorphic Buffer Layer Grown on GaAs Substrates

The results of studying the reverse dark currents of photodiodes for a wavelength of 1.06 μm grown on a GaAs substrate with the help of an InGaP metamorphic buffer layer are presented. The metalorganic chemical vapor epitaxy (MOCVD) growth technology of InGaP metamorphic buffer layers with a stepwise composition variation is developed. Photodiodes with a photosensitive area of 1 mm in diameter and radiation input through the substrate are fabricated. The photodiode dark current at room temperature and reverse bias of –3 V was 50 nA. It is assumed that the bulk component of the dark current is caused by the tunneling mechanism through the trap levels.

36 MATERIALS SCIENCE↗

DOE OSTI2018

Magnetooptics of HgTe/CdTe Quantum Wells with Giant Rashba Splitting in Magnetic Fields up to 34 T

The electron cyclotron resonance spectra in classical and quantizing magnetic fields in asymmetric heterostructures with HgCdTe/CdHgTe quantum wells with selective barrier doping are investigated. Self-consistent calculations of the energy spectra at B = 0 and Landau levels in the framework of the 8-band Kane model using the Hartree approximation are made. The strong (~10%) splitting of the cyclotron resonance line observed in weak fields is attributed to the Rashba effect in samples with inverted and normal band structures. The evolution of absorption lines upon a variation in the magnetic field is investigated up to 34 T, when the magnetic quantization already dominates over Rashba splitting.

36 MATERIALS SCIENCE↗

DOE OSTI2018

Stimulated Emission in the 1.3–1.5 μm Spectral Range from AlGaInAs Quantum Wells in Hybrid Light-Emitting III–V Heterostructures on Silicon Substrates

Hybrid laser structures with AlGaInAs quantum wells are grown by metalorganic vapor phase epitaxy on Ge/Si(100) “virtual” substrates using GaAs and InP buffer layers. Stimulated emission is achieved under optical pumping of the prepared samples in the range of 1.3–1.5 μm at liquid-nitrogen temperature. The stimulated-emission threshold is 30–70 kW/cm{sup 2}.

36 MATERIALS SCIENCE↗

DOE OSTI2018

Effect of Features of the Band Spectrum on the Characteristics of Stimulated Emission in Narrow-Gap Heterostructures with HgCdTe Quantum Wells

We report on the stimulated emission obtained in the wavelength range of 20.3–17.4 μm on the interband transitions at T = 8–50 K in HgCdTe quantum wells placed in a dielectric waveguide formed from wide-gap CdHgTe solid solution. Heterostructures with HgCdTe quantum wells are interesting for designing long-wavelength lasers operating in the wavelength range of 25–60 μm, which is not covered by currently available quantum cascade lasers. It is shown that the maximum temperature of stimulated emission is determined by the position of lateral maxima in the dispersion dependences in the first valence subband of the quantum well. Methods for suppressing nonradiative recombination in the structures with HgCdTe quantum wells are discussed.

36 MATERIALS SCIENCE↗

DOE OSTI2018

Lowering the Lasing Threshold by Doping in Mid-Infrared Lasers Based on HgCdTe with HgTe Quantum Wells

The possibility of significant lowering of the interband lasing threshold in laser structures of the mid-infrared region based on HgCdTe with HgTe quantum wells by doping with donors, which introduce δ layers near quantum wells, is proposed and analyzed. It is shown that at an optimum surface donor concentration in the δ layer of 4 × 10{sup 10} cm{sup –2} and an operating temperature of >40 K, the lasing threshold at a wavelength of 20 μm can be lowered more than twofold.

36 MATERIALS SCIENCE↗

DOE OSTI2018

Stimulated Emission at 1.3-μm Wavelength in Metamorphic InGaAs/InGaAsP Structure with Quantum Wells Grown on Ge/Si(001) Substrate

A laser structure comprising metamorphic InGaAsP layer and InGaAs quantum wells on a non-inclined Si(001) substrate with relaxed Ge buffer layer has been grown for the first time by metal-organic vapor phase epitaxy (MOVPE). The optically pumped lasers exhibit stimulated emission at a wavelength of 1.3 μm. At liquid-nitrogen temperature, the threshold power density of pumping at 0.8 μm amounted to 250 kW/cm{sup 2}.

77 NANOSCIENCE AND NANOTECHNOLOGY↗

DOE OSTI2018

Magnetooptical Studies and Stimulated Emission in Narrow Gap HgTe/CdHgTe Structures in the Very Long Wavelength Infrared Range

We investigate the prospects of HgTe/HgCdTe quantum wells for long-wavelength interband lasers (λ = 15–30 μm). The properties of stimulated emission (SE) and magnetoabsorbtion data of QWs structures with wide-gap HgCdTe dielectric waveguide provide an insight on dominating non-radiative carrier recombination mechanism. It is shown that the carrier heating under intense optical pumping is the main factor limiting the SE wavelength and intensity, since the Auger recombination is greatly enhanced when carriers populate high energy states in the valence band.

36 MATERIALS SCIENCE↗

DOE OSTI2018

Power characteristics of lasers with quantum-well waveguides and blocking layers

The power characteristics of lasers with a quantum-well (QW) waveguide are calculated based on a complex model taking into account the diffusion and drift of charge carriers, capture of electrons and holes at the QW levels, spatial distribution of radiation in the cavity, intraband absorption, and heating of the active region. Structures with doped blocking barrier layers are proposed, which allow one to decrease leakage currents to a few percent. The calculated average output power of a laser based on the GaInAs/GaAs QW heterostructure (aperture 100 μm) with a QW waveguide and a GaAsP doped blocking layer in a pulsed regime was 29 W at 80-A current pulses with a duration of 5 μs. (lasers)

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2017

Activation conductivity in HgTe/CdHgTe quantum wells at integer Landau level filling factors: Role of the random potential

Shubnikov-de Haas oscillations are studied in 8-nm-wide HgTe/CdHgTe quantum wells with an electron concentration of (1.7–13) × 10{sup 11} cm{sup –2} in the temperature range from 1.6 to 40 K. The gaps between Landau levels and the quantum relaxation time are determined from the temperature dependence of the oscillation amplitude at integer filling factors. The experimental gap values are found to be in good agreement with the results of the single-particle calculation of the level energies using the 8-band Kane model. The experimental widths of the density of states are indicative of profound screening of the exchange interaction in HgTe/CdHgTe quantum wells.

36 MATERIALS SCIENCE↗

DOE OSTI2017

On the band spectrum in p-type HgTe/CdHgTe heterostructures and its transformation under temperature variation

The magnetoabsorption and interband photoconductivity spectra of HgTe/CdHgTe quantum wells exhibiting p-type conductivity are studied at different temperatures. It is shown that, for a sample with a normal band structure, the long-wavelength edge of the spectra shifts to higher energies with temperature increase, indicating an increase of the band gap in the quantum well. For a sample with an inverted band structure, it is for the first time found that the long-wavelength cut-off shifts to lower energies due to the topological phase transition from the inverted band structure to the normal structure with temperature increase. The experimental data are in agreement with the results of theoretical band-structure calculations based on the Kane model.

36 MATERIALS SCIENCE↗

DOE OSTI2017

Peculiarities of growing InGaAs/GaAs/AlGaAs laser structures by MOCVD on Ge/Si substrates

The growth of InGaAs/GaAs/AlGaAs laser structures by MOCVD at low pressures on Si(001) substrates with a Ge epitaxial metamorphic buffer layer of various thicknesses is studied. The results of the influence of the growth temperature and incorporation of additional AlAs layers at the boundary with the Ge/Si(001) substrate on the crystalline and optical quality of the formed III–V structures are presented. It is shown that the incorporation of the AlAs/GaAs/AlAs lattice at the initial growth stages of III–V heterostructures on Ge buffer layers grown on exact Si(001) substrates makes it possible to considerably decrease the density of threading defects and, consequently, form effectively emitting laser structures. The possibility of growing strained InGaAs quantum wells on Si(001) substrates allowing stimulated radiation in a wavelength region longer than 1100 nm is shown.

36 MATERIALS SCIENCE↗

DOE OSTI2017

Dual-frequency GaAs/InGaP laser diode with a GaAsSb quantum well

The results of investigation of a metal-organic-vapor-phase-epitaxy-grown GaAsSb/GaAs/InGaP laser structure are presented. Steady two-band generation caused by spatially direct and indirect optical transitions is obtained. Observation of the sum frequency shows the effective intracavity mixing of modes in semiconductor lasers of such a type.

36 MATERIALS SCIENCE↗

DOE OSTI2017

On the stimulated emission of InGaAs/GaAs/AlGaAs laser structures grown by MOCVD on exact and inclined Ge/Si(001) substrates

GaAs/AlGaAs laser structures with InGaAs quantum wells are grown by metal-organic chemical vapor deposition (MOCVD) on exact Si(001) substrates and substrates inclined by 4° to the [011] axis with a relaxed Ge buffer layer, emitting in the transparency region of bulk silicon (the wavelength is longer than 1100 nm at room temperature). The threshold power densities of stimulated emission, observed for the structures grown on exact and inclined substrates are 45 and 37 kW/cm{sup 2}, respectively.

36 MATERIALS SCIENCE↗

DOE OSTI2016

The exciton excitations and relaxation processes in low-dimensional semiconductor heterostructures with quantum wells

The processes associated with the transfer of excitonic excitations between tunnel-uncoupled quantum wells (QW) and the influence of the local electric field were investigated in AlGaAs/GaAs heterostructures by the method of photoluminescence excitation (PLE) spectroscopy at low (4.2 K) temperature. The variation in the intensity of photoluminescence (PL) from the wider QW under resonant excitation of excitonic transition in the adjacent narrow QW has been observed. The difference in the PL maximum position and intensity of the wider QW under resonance excitation of the narrow one is explained by the influence of quantum-confined Stark effect on the process of exciton recombination.

36 MATERIALS SCIENCE↗