The experimental investigation of fluctuations is a source of information on fast and ultrafast processes responsible for HFET performance and damage. A novel fluctuation-based approach, based on hot-electron velocity fluctuations measured at a microwave frequency, is used for prediction of nitride HFET operation and failure. The following statements summarize the main results: (1) The resonance-type dependence of hot-phonon lifetime on 2DEG density is resolved from the electron velocity fluctuations; (2) ...
A novel fluctuation-based approach is applied to consider the unsolved problems in the realm of nitride heterostructure field effect transistors (HFETs). Fluctuations originate at a microscopic level and provide information on the processes responsible for device operation and degradation. The novel fluctuation-based approach is impelled by recent demonstration of strong correlation of microwave hot-electron fluctuations with frequency performance and degradation of nitride HFETs. The correlation has its genesis in the ...
Since June 2001, the Lithuanian National Time and Frequency Standard Laboratory has been responsible for the maintenance and dissemination of the national time scale UTC (LT), as well as for units of time and frequency. The Laboratory is equipped with two HP5071A atomic clocks (one with a high-performance Cs tube) and two multi-channel TTS-1 and TTS-2 GPS receivers. The TTS-2 system is fitted with a temperature-stabilized GPS antenna. For dissemination ...
This report results from a contract tasking Semiconductor Physics Institute as follows: The grantee will investigate optimizing material parameters of low-temperature grown GaAs for efficient THz emitters and detectors.
The Lithuanian National Time and Frequency Standard Laboratory is responsible for maintenance and dissemination of the national time scale UTC (LT), time and frequency units. Since June 2001, we have been contributing to TAI. The Laboratory is equipped with two HP5071A cesium atomic clocks (one with a high-performance Cs tube) and two TTS-2 multichannel GPS receivers based on Motorola VP Oncore GPS processors. One of the GPS receivers is equipped ...
Possibilities to develop the honeypot type intrusion detection systems (IDS) for databases are discussed. Two types of concept honeypot systems are suggested. Network level system is based on the emulation of the database connections and is aimed to detect intruders searching for database servers and attempting to read basic database listeners information. Honeypot type database level IDS module is aimed to react to enquiries of database tables not used by ...
This report results from a contract tasking Semiconductor Physics Institute as follows: The contractor will investigate methods of creating a fast detector of high power microwave radiation that can measure the amplitude of the pulses of nanoseconds duration in the order of 100 kW. The contractor's investigation will include: 1. Detection properties of asymmetrically shaped semiconductor structure, fabricated on the base of silicon single crystal; 2. Suitability of the device ...
This report results from a contract tasking Semiconductor Physics Institute as follows: The contractor will investigate chaotic electronic oscillators operating in the VHF and the UHF ranges. Chaos oscillators will be investigated both numerically and experimentally with the goal of developing a systematic approach toward design, active nonlinear device selection, and performance optimization. The research will encompass three aspects in both the VHF frequency range and UHF frequency range: Design ...
This report results from a contract tasking Semiconductor Physics Institute as follows: The contractor will investigate Gallium Arsenate (GaAs) based terahertz emitters. A variety of GaAs devices will be grown and characterized by standard electrical and optical techniques. The terahertz emission efficiency and its spectral width of the samples will also be measured. The goal of this investigation is to find the optimal conditions for the growth of GaAs layers ...
The electron (polar optical (PO)) phonon scattering mechanisms which determine the electron mobility in a Al(0.25)Ga(0.75) As/GaAs/Al(0.25) Ga(0.75). As quantum well (QW) with an inserted thin AlAs barrier are considered. It is shown that the decrease of the second subband electron scattering by PO-phonon emission is responsible for the large increase of the mobility in the QW with the inserted barrier.
We propose a planar diode based on a thin asymmetrically-shaped n-n(+)-GaAs junction prepared on an elastic polyimide film as THz detector. The device can be used to detect electromagnetic radiation in the range from 0.129 THz up to 2.5 THz at room temperature. The principle of operation of the device is based on non-uniform carrier heating effects caused by both the asymmetrical shape of the structure and the presence of ...
We investigate electron transport and shot noise in single barrier GaAs/AlGaAs heterostructure of nanometric sizes. The coupling between space charge and the dependence of the transmission coefficient on energy is found to provide the positive feedback which enhances shot noise and ultimately leads to a current instability of S-type. Theoretical results are in qualitative agreement with existing experiments and confirm recent Monte Carlo simulations evidencing shot-noise enhancement in GaAs/AlGaAs heterostructures. ...
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