High electron mobility transistors (HEMTs) have been developed based on InAlAs/InGaAs heterostructures on an InP substrate, with a transconductance of about 1000 mS/mm, a reverse breakdown voltage of more than 10 V and a unity-gain cutoff frequency is 140 GHz. In addition, HEMT transistors based on AlGaAs/InGaAs/GaAs heterostructures on a GaAs substrate with double gate recessing technology have been developed. This transistors demonstrate a maximum measured transconductance of the current-voltage characteristic of 520 mS/mm, a maximum drain current of 670 mA/mm, and a gate-drain breakdown voltage of 14 V and a unity-gain cut-off frequency is 120 GHz. Due to the increased breakdown voltage, the developed transistors have been used in monolithic integrated circuits of millimeter-wave power amplifiers with an output power of more than 110 mW.

Приводятся результаты теоретического и экспериментального сравнения эффективности преобразования сигналов диодами на основе сверхрешеток с малым числом периодов (N-образная вольт-амперная характеристика) и перспективными умножительными гетеробарьерными диодами (варакторами) (вольт-фарадная характеристика параболического вида). Ключевые слова: диоды на основе сверхрешеток, нелинейная вольт-амперная характеристика, варактор, вольт-фарадная характеристика параболического вида, умножители частоты сигналов.

The results of theoretical and experimental comparison of the signal-conversion efficiency by diodes based on superlattices with a small number of periods ( N -like current–voltage characteristic) and promising frequency-multiplier diodes (varactors) (parabolic capacitance–voltage characteristic) are presented.

A high-electron-mobility transistor (HEMT) based on InAlAs/InGaAs/InP heterostructures possessing higher breakdown characteristics is developed. An InGaAs composite channel structure, combined with completely selective forming of the double recess structure, is used in the devices. HEMTs with a T‑shaped gate 120 nm in length consist of four fingers, each 30 μm in width, exhibit a maximum transconductance of  810 mS/mm, 460-mA/mm maximum density of drain current and 8- to 10-V drain-to-gate breackdown voltage. The current-amplification cut-off frequency of transistors is over 115 GHz. Due to the enhanced breakdown voltage and the forming of a double recess structure by selective etching, the elaborated transistors are promising for application in the monolithic integrated circuits of the millimeter-wave medium power amplifiers.

High-electron mobility transistor (HEMT) with improved breakdown characteristics has been developed. Composite InGaAs channel structure was used in combination with fully selective double recess device fabrication process. HEMTs with T-gate length of 120 nm and width 4x30 m demonstrate maximum extrinsic transconductance of 810 mS/mm, maximum drain current density of 460 mA/mm and gate-drain reverse breakdown voltages as high as 8–10 V. Devices cut-off frequency exceed 115 GHz. Because of increased breakdown voltage and fully selective double recess fabrication process designed HEMTs are promising for medium power mm-wave MMIC amplifiers.

The influence of nonequilibrium processes in semiconductor structures under the effect of radiation on the characteristics of structures and microwave transistors based on them is analyzed. Special attention is paid to the comparison of pilot (experimental) and series-produced structures and transistors based on them before and after γ-neutron irradiation.

Narrow band emissions at 2.6–2.8 THz are observed out of liquid helium cooled 1 mm disk chips prepared of a wafer with the very low n type doped weak barrier GaAs–GaAlAs superlattice of 1000 periods. The emissions are at about 8.0–18.0 V pulsed voltage applied to the chips in region of the chips positive DC differential conductivity that guaranties absence of inhomogeneous electric field domains in the chips. The emission frequency bands are estimated with a cyclotron resonance filter; the measurements show that the band width is of about that of the THz quantum cascade laser. By using long voltage pulses the chip heating above 100 K is achieved without substantial change in emission power. We speculate that the emission is super luminescence (amplification) of whispering gallery modes in the chips as a result of inverted Wannier-Stark level transitions under bias. The results are the first world demonstration of THz stimulated emission in a simple superlattice within region of positive DC differential conductivity; they give strong impetus for development of THz and higher frequency sources based on such simple superlattices; the sources should well compete with the THz quantum cascade lasers in particular at elevated temperatures.

AbstractThe influence of nonequilibrium processes in semiconductor structures under the effect of radiation on the characteristics of structures and microwave transistors based on them is analyzed. Special attention is paid to the comparison of pilot (experimental) and series-produced structures and transistors based on them before and after γ-neutron irradiation.

The molecular-beam epitaxy of InGaAs/InAlAs/AlAs structures for heterobarrier varactors is studied and optimized. The choice of the substrate-holder temperature, growth rate and III/V ratio in the synthesis of individual heterostructure regions, the thickness of AlAs inserts and barrier-layer quality are critical parameters to achieve the optimal characteristics of heterobarrier varactors. The proposed triple-barrier structures of heterobarrier varactors with thin InGaAs strained layers immediately adjacent to an InAlAs/AlAs/InAlAs heterobarrier, mismatched with respect to the InP lattice constant at an AlAs insert thickness of 2.5 nm, provides a leakage current density at the level of the best values for heterobarrier varactor structures with 12 barriers and an insert thickness of 3 nm.

InGaAs/GaAs/AlGaAs laser diodes with quantum wells are grown by the metal-organic chemical vapor deposition (MOCVD) method on an exact Si (001) substrate with a Ge buffer layer. The diodes generate stimulated emission in the pulsed mode at room temperature in the spectral range from 1.09 to 1.11 μm.

Созданы InGaAs/GaAs/AlGaAs лазерные диоды с квантовыми ямами, выращенными методом МОГФЭ на неотклоненной Si (001)-подложке с буферным слоем Ge. Диоды генерируют стимулированное излучение в импульсном режиме при комнатной температуре в спектральном диапазоне 1.09-1.11 мкм. DOI: 10.21883/FTP.2017.11.45105.19

Представлены результаты исследований по оптимизации технологии молекулярно-пучковой эпитаксии структур InGaAs/InAlAs/AlAs для гетеробарьерных варакторов. Выбор температуры держателя подложки, скорости роста и соотношения потоков элементов III и V групп при синтезе отдельных областей гетероструктуры, толщина AlAs-вставок и качество границ барьерных слоев являются критическими параметрами для получения оптимальных характеристик гетеробарьерных варакторов. Предложенная конструкция трехбарьерных структур гетеробарьерных варакторов с непосредственно примыкающими к гетеробарьеру InAlAs/AlAs/InAlAs тонкими напряженными слоями InGaAs, рассогласованными относительно постоянной решетки подложки InP, при толщине AlAs-вставок 2.5 нм обеспечивает плотность тока утечки на уровне лучших опубликованных значений для структур гетеробарьерных варакторов с 12 барьерами и толщиной вставок 3 нм. DOI: 10.21883/FTP.2017.11.45095.09

Research from Russia presents the possibility of using a simple disc cavity laser structure for single mode vertical high emission terahertz sources, with lower costs.

Properties of disk cavities for terahertz (THz) heterostructure lasers are discussed basing on observation of emission and beam from THz quantum cascade disk laser and analytical evaluation of modes, beams and losses of the laser disk cavities. The measured laser beam has beam peak at about 30° from vertical. To find condition for vertically emitted beam and for evaluation of the laser modes, emission beams and losses simple approach adopted in theory of slit (patch) antennas is used. With this approach results on observed laser beam are discussed and a possibility to create single-frequency disk laser with narrow vertical beam. This can be achieved if only single TEM1m cavity mode is exited. Several examples of such possibility for 100 µm wavelength with disk cavities from 18 to 200 µm in diameter and with cascade thickness 10 µm are presented. Depending on the diameter the cavity emission losses are higher than or of about that of THz quantum cascade laser waveguide losses or amplification. For wavelength longer than 100 µm and (or) with lower cascade thickness, the losses go down and cavity could be optimised for creation a single-mode powerful vertically emitted disk laser.

We report on realization of the InGaAs/GaAs/AlGaAs quantum well laser grown by metallorganic chemical vapor deposition on a virtual Ge-on-Si(001) substrate. The Ge buffer layer has been grown on a nominal Si(001) substrate by solid-source molecular beam epitaxy. Such Ge buffer possessed rather good crystalline quality and smooth surface and so provided the subsequent growth of the high-quality A3B5 laser structure. The laser operation has been demonstrated under electrical pumping at 77 K in the continuous wave mode and at room temperature in the pulsed mode. The emission wavelengths of 941 nm and 992 nm have been obtained at 77 K and 300 K, respectively. The corresponding threshold current densities were estimated as 463 A/cm2 at 77 K and 5.5 kA/cm2 at 300 K.

New intraband semiconductor lasers—Wannier–Stark lasers—based on simple GaAs (150 Å, quantum well)/GaAlAs (19 Å with an aluminum fraction of 12%, barrier) superlattices have been demonstrated. The amplification mechanism in these lasers is based on population inversion between the ground Wannier–Stark level in the superlattice quantum wells and the weakly populated upper Wannier–Stark level in the wells two, three, or four periods down in the applied potential. Multiple regions of intense stimulated microwave emission near voltages of 8, 13, and 20 V (i.e., in the vicinity of resonances between these Wannier–Stark levels of the superlattice) have been discovered in the laser chips. The stimulated emission emerges in the circuit formed by the chip and its wiring. The emission from one of the chips at a temperature of up to 150 K (near 20 V applied to the chip) occurs at a frequency of about 7.3 GHz and has an estimated power of up to 1 W. It has been shown that the negative conductivity responsible for the emission still persists at 300 K but the emission is unseen owing to high losses in the circuit at this temperature. The superlattice wafer has been grown by metalorganic chemical vapor deposition. It consists of 1000 periods and a stop layer, to produce a metal–superlattice–metal terahertz resonator. Terahertz radiation has not been observed owing to a low amplification, as compared to losses in the resonator. According to the performed experiments, calculations, and discussions, such superlattices as radiation sources in gigahertz, terahertz, and higher frequency ranges could compete with quantum cascade lasers under appropriate optimization of their parameters.

A new intracavity-contacted design to realize temperature and polarization-stable high-speed single-mode 850 nm vertical cavity surface emitting lasers (VCSELs) grown by molecular-beam epitaxy is proposed. Temperature dependences of static and dynamic characteristics of the 4.5 pm oxide aperture InGaAlAs VCSEL were investigated in detail. Due to optimal gain-cavity detuning and enhanced carrier localization in the active region the threshold current remains below 0.75 mA for the temperature range within 20-90 degrees C, while the output power exceeds 1 mW up to 90 degrees C. Single-mode operation with side-mode suppression ratio higher than 30 dB and orthogonal polarization suppression ratio more than 18 dB was obtained in the whole current and temperature operation range. Device demonstrates serial resistance less than 250 Ohm, which is rather low for any type of single-mode shortwavelength VCSELs. VCSEL demonstrates temperature robust high-speed operation with modulation bandwidth higher than 13 GHz in the entire temperature range of 20-90 degrees C. Despite high resonance frequency the high-speed performance of developed VCSELs was limited by the cut-off frequency of the parasitic low pass filter created by device resistances and capacitances. The proposed design is promising for single-mode high-speed VCSEL applications in a wide spectral range.

The results of modeling the processes in high-power field-effect transistors with a two-dimensional electron gas (HEMT) when subjected to irradiation with high-energy (>100 keV) photons are reported. The possibility of using a complex of analytical and numerical models for optimizing the structure of radiation-resistant HEMT is discussed.