V. A. Smirnov

Temperature dependence of the threshold current of QW lasers

The temperature dependence of the threshold current in GaInAs-based laser structures has been studied in a wide temperature range (4.2 ≤ T ≤ 290 K). It is shown that this dependence is monotonic in the entire temperature interval studied. Theoretical expressions for the threshold carrier density are derived and it is demonstrated that this density depends on temperature linearly. It is shown that the main contribution to the threshold current comes from monomolecular (Shockley-Read) recombination at low temperatures. At T > 77 K, the threshold current is determined by radiative recombination. At higher temperatures, close to room temperature, Auger recombination also makes a contribution. The threshold current grows with temperature linearly in the case of radiative recombination and in accordance with T3 in the case of Auger recombination.

Effect of annealing on the optical and photoelectrical properties of CdxHg1 − xTe heteroepitaxial structures for the middle infrared range

We have studied the influence of various postgrowth treatments (annealing in helium atmosphere or mercury vapor, low-energy ion etching) on the optical and photoelectrical properties of mercury cadmium telluride (CdxHg1 − xTe) heteroepitaxial structures for the photo- and optoelectronic devices operating in the middle infrared range (3–5 μm). It is established that the annealing in mercury vapor is optimum for improving the photoluminescence characteristics in this range.

Field effect in a graphene oxide transistor for proton and electron–hole conductivities

Proton (wet atmosphere) and electron (reduced graphene oxide) conductivities can be observed in graphene oxide films. The field effect in a graphene oxide transistor for different conductivity types has been discovered and investigated.

Photoluminescence of CdHgTe epilayers grown on silicon substrates

We have studied the photoluminescence (PL) spectra of thin layers of mercury cadmium telluride (CdHgTe) solid solutions grown by molecular beam epitaxy on silicon substrates. It is established that a disorder in the solid solution structure in these layers does not exceed that in the layers grown by the same method on GaAs substrates. The PL spectra of CdHgTe/Si samples exhibit emission lines characteristic of the structurally perfect material, in particular, the lines due to donor-acceptor recombination and the recombination of excitons bound to impurities.

Impact-ionization-stimulated electroluminescence in isotype n-GaSb/n-AlGaAsSb/n-GaInAsSb heterostructures

We have studied electroluminescence in n-GaSb/n-AlGaAsSb/n-GaInAsSb heterostructures with isotype heterojunctions, in which the quantum efficiency of emission is increased due to the additional production of electron-hole pairs as a result of the impact ionization that takes place near the heterointerface. The impact ionization in such heterostructures is possible due to the presence of deep wells in the energy band structure.

1.5–1.8 μm photoluminescence of MBE-grown HgCdTe films

The photoluminescence (PL) of HgCdTe films grown by molecular beam epitaxy (MBE) has been studied in the 1.5–1.8 μm wavelength range. The post-growth annealing of samples for 20 h at 270°C in an inert atmosphere leads to changes in the spectrum and intensity of luminescence. The spectral changes are related to an increasing homogeneity of the film composition in depth as a result of the mutual diffusion of alloy components. An increase in the room-temperature PL intensity is due to the improved structure of annealed films.

Electrical properties of CdxHg1−xTe and ZnxCdyHg1−x−yTe modified by low-energy ion bombardment

The phenomenon of conversion of the conductivity type in p-type samples of the CdxHg1−xTe (0.28≤x≤0.55) and ZnxCdyHg1−x−yTe solid solutions bombarded by low-energy argon ions was studied. It is shown that a necessary condition for the conversion effect in CdxHg1−xTe with 0.28≤x≤0.39 is ion neutralization in the bombarding beam. The dependence of the conversion layer thickness in CdxHg1−xTe on the solid solution composition agrees with that predicted by the diffusion model of ion-bombardment-induced conversion of the conductivity type.

Electroluminescence of the unconfined heterostructure p-GaInAsSb/p-InAs at liquid-helium temperatures

The electroluminescence of the single unconfined type-II heterojunction p-GaInAsSb/p-InAs was investigated in the temperature range T=4.2–77 K. As the temperature was reduced below T=77 K, the luminescence bands with maxima at 311 meV (band A) and 384 meV (band B) were found to shift toward higher energies. At 4.2 K, the short-wave band split into two bands, B1 and B2. These results are explained in terms of a model involving recombinations of electrons from the conduction band to an acceptor level of InAs, and also recombinations of electrons and holes localized in self-consistent quantum wells on either side of the heterojunction.

Field-Effect Transistor Based on the Proton Conductivity of Graphene Oxide and Nafion Films

Proton conductivity in graphene oxide and Nafion films depending on humidity and voltages across electrodes is studied in the model of a field-effect transistor. The electrical characteristics of the films are similar to one another, but the mobility of positive charges in Nafion and the current gain are higher by 2–3 orders of magnitude compared with graphene oxide. The negative ion current in graphene-oxide films at positive bias voltage is significant compared with the proton current (up to ~10%), while it is almost lacking in Nafion films (<1%).

Numerical analysis of the energy-band diagram of type-II p-GaInAsSb/p-InAs heterojunction and size-quantization levels at the interface

The equilibrium energy-band diagram of a broken-gap p-GaInAsSb/p-InAs heterojunction was calculated by solving the Poisson equation with account of the charge of free carriers and ionized impurities and the built-in charge at the heterointerface. The quantum level energies were found within the quasi-classical approximation for electrons in the self-consistent potential well. The calculated energies are close to those observed in electroluminescence spectra of such heterojunctions.