Terahertz radiation from large aperture Si p-i-n diodes (original) (raw)
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THz generation using 800 to 1550 nm excitation of photoconductors
2009
We demonstrate the efficient generation of terahertz (THz) radiation from Fe-doped InGaAs-based photoconductive antennas. We present time-domain data showing generation of pulsed THz radiation from antennas fabricated on two different wafers, optimized to maximize the near-infrared-to-THz conversion efficiency. Detection was performed using both (110) ZnTe and GaP crystals, with pump and probe wavelengths being adjusted from 800 nm to 1550 nm using a cavity-tuned OPO pumped by a pulsed near-infrared Ti:Sapphire laser.
Terahertz emission from GaInAs p-i-n diodes photoexcited by femtosecond laser pulses
Lithuanian Journal of Physics, 2016
Lattice-matched GaInAs p-i-n diodes of different i-region thicknesses have been MBE grown on n-type InP (100) and (111) crystallographic orientation substrates. It has been found that terahertz emission from such structures when illuminated with femtosecond laser pulses can be more efficient than that from the known to date best surface terahertz emitter (111) p-InAs. The explanation of the terahertz generation mechanism from p-i-n diodes is based on ultrafast photocurrent effects. Anisotropic transient photocurrents causing the 3ϕ azimuthal angle dependence are observed in the sample on (111) substrate. These p-i-n structures allow covering a technologically important 1.55 μm range and may provide controllability and compactness of a THzTDS system when biased with an external voltage source.
THz generation using extrinsic photoconductivity at 1550 nm
Optics Express, 2012
1550-nm pulses from a fiber-mode-locked laser are used to drive an ErAs:GaAs photoconductive switch, resulting in easily measured THz radiation with average broadband (~0.1 to 1.0 THz) power of ≈0.1 mW. The new THz switching mechanism is attributed to fast extrinsic photoconductivity that generates photocarriers (probably electrons) from the ErAs nanoparticles embedded in the material with a lifetime of ~0.45 ps (354 GHz bandwidth). This is the first known demonstration of useful THz power generation by extrinsic photoconductivity.
Efficient terahertz devices based on III–V semiconductor photoconductors
IET Optoelectronics, 2014
A series of planar aperture and dipole antenna structures fabricated on low temperature grown GaAs and InP-based photoconductors have been evaluated as terahertz (THz) emitters and detectors in a time-domain spectroscopy system under pulsed excitation. The combination of large aperture antennas as emitters and short dipole antennas as detectors results in efficient THz devices operating at 800 nm, 1 μm and 1.55 μm excitation wavelengths. The system responses of these materials are among the best ever reported and allow high-quality measurements to be made. Finally, characterisation of a structure able to be biased vertically and its evaluation as THz emitter is reported for the first time. The THz response of this material with a strong THz signal at low-voltage bias makes the development of battery-operated THz devices possible.
Journal of Lightwave Technology, 2016
The design, analysis, and demonstration of flip-chip bonding packaged uni-traveling-carrier photodiodes (UTC-PDs) with THz (dc to 315 GHz) 3-dB bandwidth and high-power performance are reported. The high-frequency roll-off (up to 0.4 THz) of the flip-chip bonding structure and device heating under high power operation are both minimized through properly downscaling the area of the bonding pad and minimizing the solder distance to the active area of the miniaturized UTC-PD. In order to suppress the serious space-charge screening effect in miniaturized UTC-PDs under high-current density (∼180 kA/cm 2) operation, an n-type charge layer is inserted into the collector. The detailed dynamic measurement results of these packaged PD modules indicate that non-equilibrium electron transport plays an important role in determining the maximum speed and THz output power. In addition, a femtosecond (fs) optical pulse train generator with a ∼300 fs pulse-width output and repetition rate up to ∼0.3 THz is also developed to further boost the photo-generated THz-power. Compared with using an optical signal with a sinusoidal envelope for PD excitation, the short-pulse approach can offer a 3-dB enhancement in output power under the same output photocurrent and operating frequency (around 0.3 THz). By utilizing such an fs light source and our PD module, a continuous wave output power as high as 1 mW at an operating frequency of ∼0.3 THz is successfully demonstrated.
Generation of THz transients by photoexcited single-crystal GaAs meso-structures
Applied Physics B, 2013
We report a sub-picosecond photoresponse and THz transient generation of GaAs single-crystal mesoscopic platelets excited by femtosecond optical pulses. Our structures were fabricated by a top-down technique, by patterning an epitaxial, 500-nm-thick GaAs film grown on top of an AlAs sacrificial layer and then transferring the resulting etched away 10 9 20-lm 2 platelets onto an MgO substrate using a micropipette. The freestanding GaAs devices, incorporated into an Au coplanar strip line, exhibited extremely low dark currents and *0.4 % detection efficiency at 10 V bias. The all-optical, pumpprobe carrier dynamics analysis showed that, for 800-nmwavelength excitation, the intrinsic relaxation of photocarriers featured a 310-fs-wide transient with a 290 fs fall time. We have also carried out a femtosecond, timeresolved electro-optic characterization of our devices and recorded along the transmission line the electrical transients as short as *600 fs, when the platelet was excited by a train of 100-fs-wide, 800-nm-wavelength optical laser pulses. The platelets have been also demonstrated to be very efficient generators of free-space propagating THz transients with the spectral bandwidth exceeding 2 THz. The presented performance of the epitaxial, freestanding GaAs meso-structured photodevices makes them uniquely suitable for THz-frequency optoelectronic applications, ranging from ultrafast photodetectors to THz-bandwidth optical-to-electrical transducers and photomixers.
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.