Investigation of the terahertz emission characteristics of MBE-grown GaAs-based nanostructures (original) (raw)

Quantum dot materials for terahertz generation applications

Compact and tunable semiconductor terahertz sources providing direct electrical control, efficient operation at room temperatures and device integration opportunities are of great interest at the present time. One of the most well-established techniques for terahertz generation utilises photoconductive antennas driven by ultrafast pulsed or dual-wavelength continuous wave laser systems, though some limitations , such as confined optical wavelength pumping range and thermal breakdown, still exist. The use of quantum dot-based semiconductor materials, having unique carrier dynamics and material properties, can help to overcome limitations and enable efficient optical-to-terahertz signal conversion at room temperatures. Here we discuss the construction of novel and versatile terahertz transceiver systems based on quantum dot semiconductor devices. Configurable, energy-dependent optical and electronic characteristics of quantum-dot-based semiconductors are described, and the resonant response to optical pump wavelength is revealed. Terahertz signal generation and detection at energies that resonantly excite only the implanted quantum dots opens the potential for using compact quantum dot-based semiconductor lasers as pump sources. Proof-of-concept experiments are demonstrated here that show quantum dot-based samples to have higher optical pump damage thresholds and reduced carrier lifetime with increasing pump power.

Characterisation of InAs:GaAs quantum dot-based photoconductive THz antennas

2013 IEEE Photonics Conference, 2013

• Background, THz research and devices -Ultrafast semiconductors and photonics -The quantum-dot solution • QD photoconductive THz devices and test setups • Performance of QD-based THz sources -Pulsed operation, "traditional" Ti:Sapphire-driven -Characteristic output signals and efficiency -Long-wavelength options

Terahertz excitation of AFM-defined room temperature quantum dots

Physica E: Low-dimensional Systems and Nanostructures, 1998

The terahertz photoresponse of a single semiconductor quantum dot is measured at room temperature. Pronounced resonant tunneling and a rectified response at frequencies from 0.6 to 3 THz are observed in the I-» curve of the submicron device. We use this to demonstrate a novel approach to the study of quantum dots, in which a submicron resonant tunneling device is electrostatically defined using a conducting atomic force microscope (AFM) tip. In addition, the conducting AFM tip electrically contacts the device and serves as an antenna to couple far-infrared radiation into the dot.

Terahertz emission in quantum dots by sum frequency generation

Current Applied Physics, 2016

The second-order nonlinear susceptibility (SONS) in self-assembled InAs quantum dots (QDs), in the form of quantum disks, under applied electric field was studied. Using Feynman diagram, the relation of SONS for sum frequency generation was stated. Two cases were studied, which are the interband (IB) and intersubband (ISB) transitions with the consideration of the QD inhomogeneity, which is shown to be important in SONS calculations. For the ISB case, a resonance near 92 mm was predicted, which is important for infrared applications. Energy subbands and momentum matrix elements are shown as the main factors controlling SONS. It was found that adding some detuning to the pump will extend the wavelength by 45 mm which might applicable for Terahertz (THz) applications. Double resonance was shown to blue shifts the wavelength.

The effects of quantum dot coverage in InAs/(In)GaAs nanostructures for long wavelength emission

We present a study on the effects of quantum dot coverage on the properties of InAs dots embedded in GaAs and in metamorphic In 0.15 Ga 0.85 As confining layers grown by molecular beam epitaxy on GaAs substrates. We show that redshifted emission wavelengths exceeding 1.3 mm at room temperature were obtained by the combined use of InGaAs confining layers and high quantum dot coverage. The use of high InAs coverage, however, leads to detrimental effects on the optical and electrical properties of the structures. We relate such behaviour to the formation of extended structural defects originating from relaxed large-sized quantum dots that nucleate in accordance to thermodynamic equilibrium theories predicting the quantum dot ripening. The effect of the reduced lattice-mismatch of InGaAs metamorphic layers on quantum dot ripening is discussed in comparison with the InAs/GaAs system.

THz Superradiance from a GaAs: ErAs Quantum Dot Array at Room Temperature

Applied Sciences

We report that an ErAs quantum-dot array in a GaAs matrix under 1550 nm pulsed excitation produces cooperative spontaneous emission—Dicke superradiance—in the terahertz frequency region at room temperature. Two key points pertain to the experimental evidence: (i) the pulsed THz emission power is much greater than the continuous wave (CW) photomixing power; and (ii) the ultrafast time-domain waveform displays ringing cycles. A record of ~117 μW pulsed THz power was obtained, with a 1550 nm-to-THz power conversion efficiency of ~0.2%.

Terahertz emission from GaAs and InAs in a magnetic field

Physical Review B, 2001

We have studied terahertz (THz) emission from InAs and GaAs in a magnetic field, and find that the emitted radiation is produced by coupled cyclotron-plasma charge oscillations. Ultrashort pulses of THz radiation were produced at semiconductor surfaces by photoexcitation with a femtosecond Ti-sapphire laser. We recorded the integrated THz power and the THz emission spectrum as a function of magnetic