K. V. Marem’yanin

Electron transport and detection of terahertz radiation in a GaN/AlGaN submicrometer field-effect transistor

Electron transport and photoresponse in the terahertz range in a GaN/AlGaN field-effect transistor with the submicrometer gate (0.25 μm) and two-dimensional electron gas in the channel (the electron concentration ns = 5 × 1012 cm−2) were studied at 4.2 K. The charge-carrier mobility in the transistor’s channel μ = 3500 cm2/(V s) was determined from the dependence of the conductance on magnetic field. It is found that the dependence of photovoltage at the radiation frequency f = 574 GHz on the gate voltage (i.e., on the concentration of two-dimensional electrons) features a characteristic maximum, which is related to a resonance response of the subgate plasma in the transistor channel.

Wide-aperture detector of terahertz radiation based on GaAs/InGaAs transistor structure with large-area slit grating gate

Terahertz photoresponse of a GaAs/InGaAs transistor structure with large-area slit grating gate has been measured. Peaks in the photoresponse curve are assigned to plasmon resonances excited in the structure. More effective excitation of plasmon resonances is achieved in a grating gate structure with narrow slits, which increase the photoresponse amplitude by an order of magnitude.

Persistent photoconductivity in InAs/AlSb heterostructures with double quantum wells

Effects of persistent photoconductivity in InAs/AlSb heterostructures with the cap GaSb layer and two-dimensional electron gas in the InAs double quantum wells at T = 4.2 K are studied. From Fourier analysis of the Shubnikov-de Haas oscillations, electron concentrations in each quantum well are determined at various wavelengths of illumination and pronounced asymmetry of the structure caused by the built-in electric field is demonstrated explicitly. The self-consistent calculations of the energy profile of the double quantum well are performed and the concentrations of ionized donors on both sides of the well are determined, which provided concretization of the previously suggested mechanism of bipolar persistent photoconductivity in such structures.

Kinetics of terahertz photoconductivity in p-Ge under impurity breakdown conditions

Relaxation times of impurity photoconductivity in p-Ge samples excited by a nanosecond narrow-band source of terahertz radiation are studied at various bias voltages. It is shown that the relaxation time in prebreakdown fields increases with the applied electric field and decreases as the impurity breakdown field is exceeded. Nonmonotonic photoconductivity kinetics is observed in the studied samples differing by acceptor concentrations and degrees of compensation when approaching the impurity breakdown field.

Cyclotron resonance in HgTe/CdTe(013) narrowband heterostructures in quantized magnetic fields

Electron cyclotron resonance in HgTe/CdTe(013)-based narrowband heterostructures with a noninverted band structure in quantized magnetic fields has been investigated at different electron concentrations. Cyclotron transitions from the lower Landau levels of the conduction band have been discovered. The Landau levels have been calculated in the Kane model with the inclusion of strain. Comparison with the experimental data indicates that the energies of the observed cyclotron resonances are systematically higher than the calculated ones.

Experimental study of nonlinear mode mixing in dual-wavelength semiconductor lasers

New schemes for the generation of the sum, difference, and double frequencies in dual-wavelength injection lasers, based on an intracavity nonlinear mode mixing owing to a bulk nonlinearity, are experimentally investigated. Namely, the operation of the dual-wavelength laser diodes at the TE0 and TE1 modes, butt-joint laser diodes, and interband cascade lasers with tunnel junction are described.

A Multifrequency Interband Two-Cascade Laser

Multifrequency lasing in a new class of injection heterolasers, i.e., in an interband two-cascade laser with a tunneling p-n junction separating two active regions of quantum wells located in the same waveguide is obtained and studied. The developed laser structure with pulsed pumping provided the simultaneous emission of two first-order modes with the wavelengths of 1.063 and 0.98 μm and two third-order modes with the wavelengths of 0.951 and 0.894 μm. Due to nonlinear mixing of the modes within the laser cavity, the generation of the second harmonics and sum frequencies was observed.

Terahertz radiation generation in multilayer quantum-cascade heterostructures

I–V and radiative characteristics of multilayer quantum-cascade GaAs/AlGaAs heterostructures with a double metal waveguide are investigated. The I–V characteristics typical of the quantum-cascade lasers are seen. The observed threshold-intensity growth and narrow radiation spectrum are characteristic of laser generation. The measured radiation frequency was found to be about 3 THz, which coincides with the calculated value. Thus, fully domestic terahertz quantum-cascade lasers are demonstrated for the first time.

Frequency Shift in a System of Two Laser Diodes

An easily reproducible construction of two butt-joint laser diodes based on a GaAs/InGaAs/InGaP structure is fabricated and investigated. The construction forms a composite cavity in which about half of stimulated emissions of a long-wavelength diode transforms into emissions of a ground mode of a waveguide of a short-wavelength diode. It is found that the emission spectrum from the composite cavity is represented not only by fundamental (close) frequencies of two diodes with a power of ∼1 W, but also by their sum frequency and second harmonic with a power as high as 1 µW. The found nonlinear enrichment of the emission spectrum of a two-frequency heterolaser with a composite cavity is caused by a lattice nonlinearity of the semiconductor and allows one to plan equally effective intracavity generation of various frequencies in a far-IR range at room temperature.

Detection of Terahertz Radiation by Dense Arrays of InGaAs Transistors

Detection of terahertz radiation by GaAs transistor structures has been studied experimentally. The two types of samples under study included dense arrays of HEMTs and large-apertures detectors. Arrays consisted of parallel and series chains with asymmetric gate transistors for enhanced photoresponse on terahertz radiation. We investigated two types of wide-aperture detectors: grating gate detector, and single gate detector with bow-tie antenna. Wide-aperture detectors were symmetrical. Studies of transistor chains have shown that two essential features for this type of detector are the presence of asymmetry in the gate, and the type of connection between individual transistors themselves. Wide-aperture detectors have also been tested by narrow beams of terahertz radiation, which allows analyzing the role influence of individual parts of the detector for total sensitivity to terahertz excitation. The sensitivity and noise equivalent power of the detectors were evaluated.