The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
Most semiconductors have surface dynamics radically different from its bulk counterpart due to the surface state. However, direct observation of the surface carrier dynamics has been limited to nano structures where the surface-to-volume ratio is very high. Here, we develop a new type of terahertz (THz) nanoscopy to investigate surface dynamics of bulk semiconductors, using metallic nano gap accompanying...
Interdigitated photoconductive (IPC) switches are convenient sources and detectors for terahertz (THz) time domain spectroscopy. However, reflection of the emitted or detected radiation within the device substrate can lead to echoes that inherently limits the spectroscopic resolution achievable. In this work, we design and realize low-temperature-grown-GaAs (LT-GaAs) IPC switches for THz pulse generation...
Semiconductors nanowires have to potential to be building blocks for future nano-optoelectronic devices. We have recently demonstrated high performance THz photonic devices based on GaAs and InP nanowires. These include ultrafast optically switched modulators of THz radiation and single nanowire photoconductive detectors of THz pulses.
In this work, the concept of a solid-state amplifier based on the slow-wave interaction with drifting electron flow in a metal periodic structure is proposed for application in the low THz frequency range. Results of calculations at 330 GHz show the linear gain up to 50 dB/cm, including ohmic losses in the metal.
We report a new fully integrated THz Schottky detector based on vertically contacted high doped (1 · 1018/cm3) gallium arsenide (GaAs) by using a small diameter (100 nm) silver nanowire (NW) as air-bridge contact. Compared to Schottky diodes with evaporated metal contact it has lower capacitance (0.5 fF) for a high cut-off frequency as well as better zero-bias operation for a lower noise value.
We present a novel photoconductive terahertz source that can generate high power and broadband terahertz radiation with high optical-to-terahertz conversion efficiency. The high optical-to-terahertz conversion efficiency is achieved by confining the optical pump photons very tightly around the radiating elements of the photoconductive source. A distributed Bragg reflector and plasmonic nanostructures...
Plasmonic contact electrodes are very effective for enhancing the radiation power of photoconductive terahertz sources. Au is a preferred metal for plasmonic contact electrodes due to the high plasmonic enhancement factors it offers in the near-infrared regime. However, Au requires an adhesion layer to stick well to photoconductive substrates. We investigate the impact of the Au adhesion layer on...
THz coplanar waveguides were fabricated on quartz wafers with integrated epitaxially transferred low temperature grown gallium arsenide photoconductive switches. THz radiation was excited on-chip and transmitted through a tapering of the coplanar waveguide structure where it was focused down to ∼ 1.66μm. Theoretical modelling of the device confirms high E-field confinement and concentration.
Three dimensional chemical and structural information from an Al0.25Ga0.75As/GaAs terahertz quantum cascade laser heterostructure obtained by atom probe tomography is used to demonstrate the impact of diffusion-induced chemical roughening of the AlGaAs barrier layers on the optoelectronic characteristics of the laser by recalculating the band structure of the QCL and comparing the relevant parameters...
A new type of continuous-wave (CW) terahertz (THz) photomixer was fabricated using a nitrogen-doped single layer graphene (N+SLG) powder and silver nanowire (Ag-NW of Ø 300 nm) on low-temperature-grown (LTG) GaAs. The new hybrid (N+SLG/Ag-NW) structure provides simple fabrication steps and better performance in terms of high current handling together with reliable operation. The THz output power itself...
The experimental results on the effect of an electron-hole plasma on the THz generation in GaAs NWs grown by MOVPE are presented. It is shown that the dynamics of photoexcited charge carriers in nanowires is determined by the transport of charge carriers — electrons and holes and by the capture time of electrons and holes onto the surface levels. The dependence of initial fall time of THz emission...
Ultrafast photoconductive switches were fabricated from GaAs embedded with ErAs nanoparticles and tested in two antenna types: a self-complementary square spiral, and a slot antenna designed for half-wave resonance at 567 GHz. These devices are designed for driving with 1550nm lasers. At least ∼46 μW of THz average power was generated from the spiral, and ∼5 μW from the resonant slot. This is the...
We present an experimental investigation of the nonlinear response of acceptor impurities in semiconductors to coherent excitation with intense THz fields. In Zn-doped GaAs, we observed a well-defined saturation of the transition from the impurity ground state to the excited states and valence band. In B-doped Si, however, there is a clear indication of field-induced distortion of the impurity energy...
We compare the emission power of GaAs, InGaAs and InAs as function of excitation photon energy. We find that the carrier excess excitation energy is more relevant to explain their performance difference than their mobilities. We conclude that ballistic transport after photoexcitation is the dominant mechanism for terahertz emission and that the relative importance of drift current in comparison to...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.