Influence of Substrate Material on Radiation Characteristics of THz Photoconductive Emitters (original) (raw)
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IEEE Journal of Selected Topics in Quantum Electronics, 2008
We report on scalable photoconductive antennas for both emission and detection of terahertz (THz) radiation. The concept yields THz emitters with high efficiencies for the conversion of near-infrared into far-infrared radiation, and provides detectors that do not require tight focusing of both the THz beam and the near-infrared gating beam. GaAs substrates implanted with dual energy implants of N + and As + ions of various doses are compared with semiinsulating (SI) and low-temperature-grown GaAs. We discuss which material properties are desirable for emitters and detectors and identify which material is optimal as either emitter or detector substrate. Best results for detectors are found for implanted samples with doses in the range of 10 13 cm −2 for GaAs:N and for LT-GaAs. Best emitters for typical excitation conditions with a Ti:sapphire oscillator system are based on SI-GaAs.
Journal of Infrared, Millimeter, and Terahertz Waves, 2017
We investigate the influence of the surface properties of a low-temperature-grown GaAs photoconductive antenna on the terahertz (THz) emission strength, using a specially designed THz time-domain spectroscopy system. The system allows us to excite six different positions along the 10 μm gap of a coplanar stripline antenna with a length of 10 mm without changing the alignment of the optical or THz beam path. A comparison to the surface roughness and the grain size which are extracted from an atomic force and a scanning electron microscope is given.
KnE Energy, 2018
The design and technological conditions for manufacturing photoconductive antennas based on low-temperature-grown gallium arsenide (LT-GaAs) have been developed. An optimized photoconductive THz antenna based on LT-GaAs with flag geometry of the contacts was fabricated. LT-GaAs samples were obtained by molecular-beamepitaxy at temperatures of 230 ∘ C on GaAs (100) substrates. On an optical setup with a femtosecond titanium-sapphire laser, a volt (watt)-ampere characteristics and photocurrent efficiency of the photo-conductive antenna measured by the pyroelectric sensor. The optimum annealing temperature of LT-GaAs was determined for generation of intense THz radiation. PCA have been tested in the terahertz radiation generation. The substantial effect of water vapor in the air and the environment of transparent objects is THz. The useful terahertz bandwidth extends from 0.1 to 2.7 THz and the source of terahertz wave is the most commonly used nonlinear crystal ZnTe in the biomedicine applications. However, in comparison PCA on LT-GaAs with ZnTe have better results in the intensity and the power of the THz response. Therefore, it will be possible to detect a lower concentration of biological objects.
Strong emission of THz radiation from GaAs microstructures on Si
AIP Advances
Remarkably strong emission of terahertz radiation from illuminated GaAs microstructures on a Si substrate is reported. The peak-to-peak amplitude of terahertz radiation from the sample is 9 times larger than that of THz radiation from a semi-insulating GaAs wafer. The spectral width of the sample is larger than that of a semi-insulating GaAs wafer; in particular, the spectral amplitude increases at higher frequencies. The presented GaAs microstructures on a Si substrate can be suitable for practical and efficient THz sources required in various THz applications.
Technical Physics Letters, 2018
Low-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.
ETRI Journal, 2014
In this letter, we present low-temperature grown GaAs (LTG-GaAs)-based photoconductive antennas for the generation and detection of terahertz (THz) waves. The growth of LTG-GaAs and the annealing temperatures are systematically discussed based on the material characteristics and the properties of THz emission and detection. The optimum annealing temperature depends on the growth temperature, which turns out to be 540°C to 580°C for the initial excess arsenic density of 2×10 19 /cm 3 to 8×10 19 /cm 3 .
Electrical and Radiation Characteristics of Semilarge Photoconductive Terahertz Emitters
IEEE Transactions on Microwave Theory and Techniques, 2004
We present experimental characterization of semilarge photoconductive emitters, including their electrical/photoconductive parameters and terahertz spectra. A range of emitters were studied and fabricated on both LT-GaAs and SI-GaAs, having a variety of electrode geometries. The spatial cone of terahertz radiation was defined. The dependencies of the photocurrent and the terahertz power on the bias voltage and the laser power were determined. A Fourier-transform interferometer is used to determine the terahertz spectra and to clarify the effects of the substrate and electrode geometry.
Semiconductor Science and Technology, 2006
We report the coherent generation and detection of terahertz radiation from antenna-type devices made by using proton-bombarded GaAs photoconductive materials. Our combined emitter/detector setup allows us to obtain a large bandwidth going from 0.1 up to 2 THz. We compare the performance of antenna emitters fabricated using mono-and multi-energy proton implantation in semi-insulating GaAs. Improved emission of terahertz radiation with a comparable bandwidth has been obtained using multi-energy proton implantation. Our results show that creating more defects in the optical absorption region gives rise to higher damage threshold biasing and larger saturation optical pumping power levels.