The optical constants, at elevated temperatures, of some potential window materials for high power and plasma diagnostic applications

1993 ◽  
Author(s):  
J. R. Birch
Keyword(s):  
High Power ◽  
Optical Constants ◽  
Elevated Temperatures ◽  
Plasma Diagnostic ◽  
Diagnostic Applications

High‐power, twin‐frequency FIR lasers for plasma diagnostic applications

1986 ◽  
Vol 57 (8) ◽  
pp. 1986-1988 ◽  
Author(s):  
T. Lehecka ◽  
R. Savage ◽  
R. Dworak ◽  
W. A. Peebles ◽  
N. C. Luhmann ◽  
...  
Keyword(s):  
High Power ◽  
Plasma Diagnostic ◽  
Fir Lasers ◽  
Diagnostic Applications

In-situ Measurement of GaAs Optical Constants and Surface Quality, as Functions of Temperature

1991 ◽  
Vol 222 ◽  
Author(s):  
Huade Yao ◽  
Paul G. Snyder
Keyword(s):  
Room Temperature ◽  
Optical Constants ◽  
Molecular Beam ◽  
Elevated Temperatures ◽  
Native Oxide ◽  
Time Data ◽  
Gaas Sample ◽  
Optical Thermometer ◽  
Surface Changes

ABSTRACTIn-situ spectroscopic ellipsometry (SE) was applied to monitor GaAs (100) surface changes induced at elevated temperatures inside an ultrahigh vacuum (UHV) chamber (<1×10−9 torr base pressure, without As overpressure). The real time data showed clearly the evolution of the native-oxide desorption at ∼577°C, on a molecular-beam-epitaxy (MBE)-grown GaAs (100) surface. In addition, surface degradation was found before and after the oxide desorption. A clean and smooth surface was obtained from an arsenic-capped, MBE-grown GaAs sample, after the arsenic coating was evaporated at ∼350 °C inside the UHV. Pseudodielectric functions <ε>GaAs, from 1.6 eV to 4.5 eV, were obtained through the SE measurements, from this oxide-free surface, at temperatures ranging from room temperature (RT) to ∼610 °C. These <ε> data were used as reference data to develop an algorithm for determining surface temperatures from in-situ SE measurements, thus turning the SE instrument into a sensitive optical thermometer.

Junction Field Effect Transistors For High-Temperature Or High-Power Electronics

1997 ◽  
Vol 483 ◽  
Author(s):  
J. C. Zolperw
Keyword(s):  
High Temperature ◽  
High Power ◽  
Field Effect ◽  
Elevated Temperatures ◽  
Field Effect Transistors ◽  
Current Gain ◽  
Semiconductor Interface ◽  
Transistor Channel ◽  
Semiconductor Junction ◽  
Junction Field Effect Transistors

AbstractJunction field effect transistors (JFETs) are attractive for high-temperature or highpower operation since they rely on a buried semiconductor junction, and not a metal semiconductor interface as in a metal semiconductor (MESFET) or heterojunction field effect transistor (HFET), for modulating the transistor channel. This is important since a metal/semiconductor interface often degrades at elevated temperatures, either due to the ambient temperature or to Joule heating at high current levels, while a buried semiconductor junction can withstand higher temperatures. In fact, for proper design, the JFET becomes limited by thermal carrier generation in the semiconductor and not metallurgical degradation of the gate electrode.In this talk an overview is given of JFET technology based on GaAs, SiC, and GaN. While impressive room temperature, high-frequency, results have been reported for GaAs JFET's with unit current gain cut-off frequencies up to 50 GHz, more work is needed to limit substrate conduction for optimum operation at 300 °C and above. For SiC JFETs, well behaved transistor operation has been maintained up to 600 °C, however, increased frequency performance is needed. More recently, a GaN JFET has also been demonstrated that is promising for similarly high temperature operation but is presently limited by buffer conduction. Future directions for each of these technologies, and potential extension to high power switching devices such as thyristors, will be presented at the conference.

Optical Constants Retrieval from a Thin Film at Elevated Temperatures Using Emittance

2021 ◽  
Author(s):  
Jui-Yung Chang ◽  
Yi-Hua Yang ◽  
Vikas Yadav ◽  
Yu-Bin Chen
Keyword(s):  
Thin Film ◽  
Refractive Index ◽  
Thermal Radiation ◽  
Optical Constants ◽  
Elevated Temperatures ◽  
Emission Angle ◽  
Face Centered Cubic ◽  
Hexagonal Close Packed ◽  
Phase Temperature ◽  
Face Centered

Abstract Refractive index and extinction coefficient (optical constants) are essential in photonic design and thermal radiation utilization. These constants vary with the material phase, temperature, wavelength, and subject dimension. Precisely retrieving these constants of a thin film is thus challenging at elevated temperatures. To tackle this challenge, a methodology for retrieval using emittance at different emission angle θ has been developed here. The method contains four steps and takes advantages of an emissometry. The method is firstly validated using simulation and then demonstrates its feasibility by retrieving optical constants of a phase change germanium-antimony-tellurium (Ge2Sb2Te5, GST) film. Emittance from samples at 100°C, 200°C, 300°C, and 400°C is measured at θ = 0°, 15°, and 30°. The spectral range of retrieval covers from 4 μm to 18 μm where thermal radiation dominates. The investigated film phase considers amorphous, face-centered cubic (FCC), and hexagonal close packed (HCP). The retrieved constants exhibit temperature and substrate independence, but they show up significant phase reliance.

Flexible hybrid piezo/triboelectric energy harvester with high power density workable at elevated temperatures

2020 ◽  
Vol 8 (24) ◽  
pp. 12003-12012 ◽  
Author(s):  
Yanhua Sun ◽  
Yun Lu ◽  
Xiaoning Li ◽  
Zheyin Yu ◽  
Shujun Zhang ◽  
...  
Keyword(s):  
Power Density ◽  
High Power ◽  
Energy Harvester ◽  
Elevated Temperatures ◽  
Mechanical Energy ◽  
Broad Temperature Range ◽  
High Power Density ◽  
Temperature Range ◽  
Energy Harvesters ◽  
High Output

Eco-friendly energy harvesters with high output for effectively harvesting mechanical energy over a broad temperature range.

Temperature Dependence of Breakdown Field in p-π-n GaN Diodes

1998 ◽  
Vol 512 ◽  
Author(s):  
A. Osinsky ◽  
M. S. Shur ◽  
R. Gaska
Keyword(s):  
Temperature Dependence ◽  
High Power ◽  
Elevated Temperatures ◽  
Electric Breakdown ◽  
Breakdown Field ◽  
Power Devices ◽  
Avalanche Photodetectors

ABSTRACTWe present the results of the study of the electric breakdown in p-π-n GaN diodes. The breakdown is observed at reverse biases above 40 V and is accompanied by the formation of microplasmas. The study shows that the observed breakdown field in GaN (on the order of 1 to 2 MV/cm) increases with the temperature. This feature makes GaN very promising for high power devices and avalanche photodetectors, operating at elevated temperatures.

scholarly journals Novel Dual Beam Cascaded Schemes for 346 GHz Harmonic-Enhanced TWTs

Electronics ◽  
2021 ◽  
Vol 10 (2) ◽  
pp. 195
Author(s):  
Ruifeng Zhang ◽  
Qi Wang ◽  
Difu Deng ◽  
Yao Dong ◽  
Fei Xiao ◽  
...  
Keyword(s):  
High Power ◽  
Peak Power ◽  
Low Cost ◽  
High Harmonic ◽  
Harmonic Signal ◽  
Input Power ◽  
Plasma Diagnostic ◽  
Dual Beam ◽  
Thz Sources ◽  
Simulation Results

The applications of terahertz (THz) devices in communication, imaging, and plasma diagnostic are limited by the lack of high-power, miniature, and low-cost THz sources. To develop high-power THz source, the high-harmonic traveling wave tube (HHTWT) is introduced, which is based on the theory that electron beam modulated by electromagnetic (EM) waves can generate high harmonic signals. The principal analysis and simulation results prove that amplifying high harmonic signal is a promising method to realize high-power THz source. For further improvement of power and bandwidth, two novel dual-beam schemes for high-power 346 GHz TWTs are proposed. The first TWT is comprised of two cascaded slow wave structures (SWSs), among which one SWS can generate a THz signal by importing a millimeter-wave signal and the other one can amplify THz signal of interest. The simulation results show that the output power exceeds 400 mW from 340 GHz to 348 GHz when the input power is 200 mW from 85 GHz to 87 GHz. The peak power of 1100 mW is predicted at 346 GHz. The second TWT is implemented by connecting a pre-amplification section to the input port of the HHTWT. The power of 600 mW is achieved from 338 GHz to 350 GHz. The 3-dB bandwidth is 16.5 GHz. In brief, two novel schemes have advantages in peak power and bandwidth, respectively. These two dual-beam integrated schemes, constituted respectively by two TWTs, also feature rugged structure, reliable performance, and low costs, and can be considered as promising high-power THz sources.

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