I. G. Malkina

Transport anisotropy in spontaneously ordered GaInP2 alloys

Large anisotropy in minority carrier diffusion length and specific conductivity is observed in epitaxial layers of GaInP2 alloys with CuPtB-type ordering. Both the diffusion length and specific conductivity are enhanced, by factor of 10, in the [110] direction, parallel to the line of intersection of the ordered (1–11) and (−111) planes with the (001) growth surface. The reduction in transport length in the [1–10] direction is attributed to carrier scattering at domain boundaries. No transport anisotropy is observed in disordered GaInP2 epitaxial layers.

Spectroscopy of layers of InAs in GaAs across the transition from layered to three-dimensional growth

Changes in the photoluminescence spectra and photoelectric phenomena at the transition from layered to three-dimensional growth with the formation of quantum dots were traced in samples with continuously increasing effective thickness of the strained layer.

Photoelectric properties of GaAs/InAs heterostructures with quantum dots

The capacitive photovoltage and photoconductivity spectra of GaAs/InAs heterostructures with quantum dots is discussed. For these structures, which were fabricated by metallorganic gas-phase epitaxy, the photosensitivity spectrum has a sawtoothed shape in the wavelength range where absorption by the quantum dots takes place, which is characteristic of a δ-function-like density of states function. The spectra also exhibit photosensitivity bands associated with the formation of single-layer InAs quantum wells in the structure. An expression is obtained for the absorption coefficient of an ensemble of quantum dots with a prespecified size distribution. It is shown that the energy distribution of the joint density of states, the surface density of quantum dots, and the effective cross section for trapping a photon can all be determined by analyzing the photosensitivity spectrum based on this assumption.

Infrared radiation from hot holes during spatial transport in selectively doped InGaAs/GaAs heterostructures with quantum wells

The infrared radiation from hot holes in InxGa1−xAs/GaAs heterostructures with strained quantum wells during lateral transport is investigated experimentally. It is found that the infrared radiation intensities are nonmonotonic functions of the electric field. This behavior is due to the escape of hot holes from quantum wells in the GaAs barrier layers. A new mechanism for producing a population inversion in these structures is proposed.

Low temperature transport properties of InAs/GaAs structures with quantum dots

Abstract The transport and optical properties of InAs/GaAs structures with quantum dots have been investigated as a function of InAs content. Photoluminescence (PL) spectra showed polarization of radiation in the plane of the structures. The temperature dependence of the resistance was measured in the [110] and [−110] directions in the temperature range 4.2 K–300 K and anisotropy of conductivity was found. The Shubnikov de Haas effect, magnetoresistance ρ ( B ) and the Hall effect have been measured in a magnetic field B up to 10 T.

Far-infrared emission and possibility of population inversion of hot holes in MQW InGaAs/GaAs heterostructures under real space transfer

Abstract Hot holes in strained MQW In x Ga 1− x As/GaAs heterostructures excited at lateral charge transport are probed by far-infrared emission and band gap photoluminescence. Highly nonequilibrium phenomena discovered are shown to result from the real space transfer. New mechanism for the population inversion between continuum and shallow bound states in quantum wells in high lateral electric fields is put forward.

Polarization of in-plane photoluminescence from InAs/Ga(In)As quantum-well layers grown by metallorganic vapor-phase epitaxy

This paper investigates the linear polarization of photoluminescence emitted along the plane of an InAs/Ga(In)As wafer. The polarization was observed to depend on the asymmetry of the quantum-well shape, quantum-dot formation, and the presence of inclusions in the bulk alloy.

Modelling Quantum Well Laser Diode Structures

Many of the attractions of quantum wells in lasers derive from the properties of the density of states function of the two-dimensional electron system. The abrupt edge of the density of states as a function of energy provides a very high differential gain above transparency leading to significant reductions in threshold current in appropriately designed devices compared with their bulk counterparts. The effective density of states of a two-dimensional system has a linear dependence upon temperature which leads directly to an intrinsic linear temperature dependence of threshold current compared with the stronger “three-halves” dependence of a bulk material. Because of the benefits of these characteristics of the two-dimensional system, much of the modelling of quantum well lasers has understandably concentrated on the intrinsic gain-current characteristic of the quantum well active region. These calculations usually use an ideal, square, potential well and extrinsic non-radiative currents are neglected. In devices operating at wavelengths below about 1µm, where intrinsic Auger recombination is negligible, this approach has been reasonably successful in predicting trends in the room temperature threshold current with respect to parameters such as well width or cavity length. This is particularly true for the GaAs/A1GaAs material system which can be grown free of significant concentrations of non-radiative recombination centres.

GaAsSb/GaAs quantum well growth by MOCVD hydride epitaxy with laser sputtering of antimony

A new method of obtaining quantum-size GaAs1−xSbx (x⩽0.45) layers is proposed. The method consists in laser vaporization of solid metallic antimony near the substrate directly in the reactor. The antimony concentration is set by the antimony sputtering time with the arsine flux shut off. The polarization of the photoluminescence of the obtained layers indicates the formation of quantum wires. The heterostructures obtained are used to fabricate laser diodes.

Electron mobility in selectively doped GaAs/InxGa1-xAs multiple quantum well structures

The photoluminescence, the temperature dependence of the electrical conductivity (0.4<T<300 K), the magnetoresistance and the Hall effect were investigated in selectively doped GaAs/InxGa1−xAs multiple quantum well (MQW) structures. The dependencies of the electron mobility on the width of the quantum wells and on temperature were measured. It is shown that in narrow MQW structures the value of mobility is restricted by interface roughness scattering. In wider MQW structures, the alloy scattering has a detrimental effect on the low magnetic field transport properties. A negative magnetoresistance was observed in low magnetic fields. From a detailed comparison between theory of weak localisation and experiment the wave function relaxation time τϕ and its temperature dependence were evaluated. The quantum Hall effect was investigated in all samples in the temperature interval 0.4 K ÷ 4.2 K in magnetic fields up to 40 T.