We report on a high-sensitive THz plasmonic-enhanced photoconductive antenna (PCA)-detector based on an InGaAs/InAlAs superlattice heterostructure. A noticeable increase in the sensitivity and signal-to-noise ratio of the proposed PCA-detector is shown compared to a similar detector without plasmonic electrodes. The efficiency of plasmonic electrodes has been experimentally confirmed via pulsed THz time-domain spectroscopy by measuring the dependence of the THz amplitude of the detector’s signal on the polarization of laser excitation.

The parameters of the generated terahertz radiation in a two-dimensional WSe2 film grown by chemical vapor deposition were investigated for the first time. The main mechanism of the generated terahertz radiation in the studied sample was determined. The terahertz amplitude dependence on azimuthal angle in the two-dimensional WSe2 film was studied. The distribution of the laser pump electric field in the WSe2 / SiO2 / Si structure was calculated as a function of the silicon dioxide thickness. The choice of the optimal structural geometry for the effective generation of terahertz radiation by a monolayer WSe2 was theoretically justified

AbstractThe influence of excitation photons energy on the relaxation times of photoexcited carriers is studied. The involved relaxation mechanisms are evaluated and the reflection coefficient of the InGaAs/InAlAs superlattice heterostructures is analyzed. A model is built for the reflection coefficient of the InAlAs barrier layer, depending on the excitation photons energy. The resonance behavior of the reflection coefficient is explained.

AbstractLow-temperature gallium arsenide (LT-GaAs) films were grown by the method of molecularbeam epitaxy (MBE) at a reduced temperature (230°C) on GaAs(100) substrates and subjected to postgrowth annealing in various regimes. Photoconductive antennas (PCAs) with flag geometry formed on the film surface were characterized by terahertz (THz) response power at various bias voltages. The method of THz spectroscopy was used to study the characteristics of PCAs based on LT-GaAs films annealed in various regimes and the optimum interval of postgrowth annealing temperatures (670–720°C) was established.

AbstractThe results of experimental studies of the time dynamics of photoexcited charge carriers in In_0.53Ga_0.47As/In_0.52Al_0.48As superlattices grown by molecular-beam epitaxy on a GaAs substrate with a metamorphic buffer are reported. On the basis of the results of the numerical simulation of band diagrams, the optimal thickness of the In_0.52Al_0.48As barrier layer (4 nm) is chosen. At this thickness, the electron wave functions in In_0.53Ga_0.47As substantially overlap the In_0.52Al_0.48As barriers. This makes it possible to attain a short lifetime of photoexcited charge carriers (τ ~ 3.4 ps) at the wavelength λ = 800 nm and the pumping power 50 mW without doping of the In_0.53Ga_0.47As layer with beryllium. It is shown that an increase in the wavelength to λ = 930 nm (at the same pumping power) yields a decrease in the lifetime of photoexcited charge carriers to τ ~ 2 ps. This effect is attributed to an increase in the capture cross section of trapping states for electrons with lower energies and to a decrease in the occupancy of traps at lower excitation densities.

Методами оптического зондирования при фемтосекундной лазерной накачке (optical pump-probe) и терагерцевой спектроскопии во временной области исследовано влияние эпитаксиальных напряжений на динамику неравновесных носителей заряда, а также спектр терагерцевого излучения в пленках InyGa1-yAs. Продемонстрировано снижение времени жизни неравновесных носителей заряда и увеличение ширины спектра терагерцевого излучения для пленки InyGa1-yAs с большим механическим напряжением. DOI: 10.21883/PJTF.2017.22.45260.16958