V. E. Zemlyakov

High-responsivity terahertz detection by on-chip InGaAs/GaAs field-effect-transistor array

Terahertz detection by a one-dimensional dense array of field-effect transistors (FETs) is studied experimentally. Such terahertz detector demonstrates greatly enhanced responsivity without using supplementary antenna elements because a short-period grating formed by metal contact fingers of densely ordered transistors in the array serves as an effective antenna coupling incident terahertz radiation to the transistor channels. Asymmetrical position of the gate contact in each FET in the array enables strong photovoltaic response.

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.

Detection of terahertz radiation by tightly concatenated InGaAs field-effect transistors integrated on a single chip

A tightly concatenated chain of InGaAs field-effect transistors with an asymmetric T-gate in each transistor demonstrates strong terahertz photovoltaic response without using supplementary antenna elements. We obtain the responsivity above 1000 V/W and up to 2000 V/W for unbiased and drain-biased transistors in the chain, respectively, with the noise equivalent power below 10−11 W/Hz0.5 in the unbiased mode of the detector operation.

Effect of nonuniform current injection on electroluminescence spectra of InGaN-GaN blue-green light-emitting diode

Blue-green InGaN/GaN light-emitting diodes (LEDs) with spatially nonuniform current injection were fabricated and tested. Broad electroluminescence (EL) spectra with equal peak intensities of blue and green emission lines and shallow trough between them were observed at elevated injected current. These features of EL-spectrum are believed to be caused by the mesh-like patterning of the electrode as it creates spatially nonuniform electric potential which provides spatial modulation of the injected current along the QW-planes. The latter results not only in spatial nonuniformity of intensity of generated light along the QW-planes but due to screening of polarization field in the QWs causes also position-dependent blue shift of EL. The observed phenomenon can be used to control the EL spectra of dual-wavelength LEDs by the patterned electrodes.

A study of the effect of the structure of plasma-chemical silicon nitride on its masking properties

Dependence of the chemical composition of a film of plasma-chemical silicon nitride on the technological parameters of the deposition process is studied. The stages in which the process parameters are optimized in order to improve the masking properties of the film are described. A systematic study of the Fourier-transform infra-red (IR) spectra of plasma-chemical silicon-nitride films is carried out. It is found that the chemical resistance of a silicon-nitride film depends on the configuration in which hydrogen is incorporated into chemical bonds.

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.

Investigation of wide-aperture plasmonic detectors by a tightly focused terahertz beam

Terahertz response of wide-aperture plasmonic detectors is studied experimentally by using a focused terahertz radiation with frequencies 1.63, 1.89 and 2.55 THz. Two different types of plasmonic detector have been investigated: (i) field-effect transistor (FET) with a grating-gate of large (2?2 mm2) area and (ii) FET with a single gate and ohmic contacts forming a bow-tie antenna. By raster scanning the detector area by using a tightly focused terahertz beam, we studied the contribution of individual parts of the detector to the total detection response and we determined the effective area of the detector structures.

Terahertz detector with series connection of asymmetric gated transistors

Terahertz (THz) detection by a one-dimensional array of series connected field-effect transistors (FETs) is studied experimentally. Such terahertz detector demonstrates greatly enhanced voltaic responsivity up to 2 kV/W. Asymmetrical position of the gate contact in each FET in the array enables strong photovoltaic response.