The impact of interfacial Si contamination on GaN-on-GaN regrowth for high power vertical devices

2021 ◽  
Vol 118 (22) ◽  
pp. 222104
Author(s):  
Kai Fu ◽  
Houqiang Fu ◽  
Xuguang Deng ◽  
Po-Yi Su ◽  
Hanxiao Liu ◽  
...  
Keyword(s):  
High Power ◽  
The Impact

The impact of photodarkening on mode instabilities in high-power fiber laser systems

2014 ◽  
Author(s):  
Cesar Jauregui ◽  
Hans-Jürgen Otto ◽  
Norbert Modsching ◽  
Oliver de Vries ◽  
Jens Limpert ◽  
...  
Keyword(s):  
Fiber Laser ◽  
High Power ◽  
Laser Systems ◽  
The Impact

Improved Heat Dissipation and Optical Performance of High-power LED Packaging with Sintered Nanosilver Die-attach Material

2010 ◽  
Vol 2010 (DPC) ◽  
pp. 001585-001605 ◽  
Author(s):  
Paul Panaccione ◽  
Tao Wang ◽  
Guo-Quan Lu ◽  
Xu Chen ◽  
Susan Luo
Keyword(s):  
Thermal Resistance ◽  
High Power ◽  
Heat Removal ◽  
High Current ◽  
Die Attach ◽  
High Power Led ◽  
Silver Epoxy ◽  
The Difference ◽  
Nanosilver Paste ◽  
The Impact

Heat removal in packaged high-power light-emitting diode (LED) chips is critical to device performance and reliability. Thermal performance of LEDs is important in that lowered junction temperatures extend the LED's lifetime at a given photometric flux (brightness). Optionally, lower thermal resistance can enable increased brightness operation without exceeding the maximum allowable Tj for a given lifetime. A significant portion of the junction-to-case thermal resistance comes from the joint between chip and substrate, or the die-attach layer. In this study, we evaluated three different types of leading die-attach materials; silver epoxy, lead-free solder, and an emerging nanosilver paste. Each of the three was processed via their respective physical and chemical mechanisms: epoxy curing by cross-linking of polymer molecules; intermetalic soldering by reflow and solidification; and nanosilver sintering by solid-state atomic diffusion. High-power LED chips with a chip area of 3.9 mm2 were attached by the three types of materials onto metalized aluminum nitride substrates, wire-bonded, and then tested in an electro-optical setup. The junction-to-heatsink thermal resistance of each LED assembly was determined by the wavelength shift methodology, described in detail in this paper. We found that the average thermal resistance in the chips attached by the nanosilver paste was the lowest, and it is the highest from the chips attached by the silver epoxy: the difference between the two was about 0.7°C/W, while the difference between the sintered and soldered was about 0.3°C/W. The lower thermal resistance in the sintered joints is expected to significantly improve the photometric flux from the device. Simple calculations, excluding high current efficiency droop, predict that the brightness improvement could be as high as 50% for the 3.9 mm2 chip. The samples will be functionally tested at high current, in both steady-state and pulsed operation, to determine brightness improvements, including the impact of droop. Nanosilver die-attach on a range of chip sizes up to 12 mm2 are also considered and discussed.

Investigation of Bipolar Degradation of 1.2 kV BJTs under Different Current and Temperature Conditions

2020 ◽  
Vol 1004 ◽  
pp. 464-471
Author(s):  
Sarah Rugen ◽  
Siddarth Sundaresan ◽  
Ranbir Singh ◽  
Nando Kaminski
Keyword(s):  
Silicon Carbide ◽  
High Voltage ◽  
Current Density ◽  
High Power ◽  
Stacking Faults ◽  
Bipolar Junction Transistors ◽  
Mode Operation ◽  
Different Temperatures ◽  
Current Densities ◽  
The Impact

Bipolar silicon carbide devices are attractive for high power applications offering high voltage devices with low on-state voltages due to plasma flooding. Unfortunately, these devices suffer from bipolar degradation, which causes a significant degradation of the on-state voltage. To explore the generation of stacking faults, which cause the degradation, the impact of the current density and temperature on bipolar degradation is investigated in this work. The analysis is done by stressing the base-collector diode of 1.2 kV bipolar junction transistors (BJTs) as well as the BJTs in common-emitter mode operation with different current densities at different temperatures.

High power laser machines – a game changer in the field of endourology? The impact of stone density on laser time using Lumenis laser p120 compared to standard 20w laser

2019 ◽  
Vol 18 (1) ◽  
pp. e492-e493
Author(s):  
M. Mekayten ◽  
A. Lorber ◽  
I. Katafigiotis ◽  
I. Leotsakos ◽  
S. Sfouggaristos ◽  
...  
Keyword(s):  
High Power ◽  
High Power Laser ◽  
Power Laser ◽  
The Impact ◽  
Stone Density ◽  
Game Changer

scholarly journals High-Porosity Thermal Barrier Coatings from High-Power Plasma Spray Equipment—Processing, Performance and Economics

Coatings ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 957
Author(s):  
Nicholas Curry ◽  
Matthias Leitner ◽  
Karl Körner
Keyword(s):  
Thermal Barrier Coatings ◽  
High Power ◽  
Deposition Efficiency ◽  
Sintering Behavior ◽  
Thermal Barrier ◽  
Low Density ◽  
High Porosity ◽  
Plasma System ◽  
Barrier Coatings ◽  
The Impact

High-porosity thermal barrier coatings are utilized on gas turbine components where maximizing the coating thermal insulation capability is the primary design criteria. Though such coatings have been in industrial use for some time, manufacturing high-porosity coatings quickly and efficiently has proven challenging. With the industry demand to increase productivity and reduce waste generation, there is a drive to look at improved coating manufacturing methods. This article looks at high-porosity coatings manufactured using a high-power plasma system in comparison with a current industrial coating. A commercial spray powder is compared with an experimental Low-Density powder developed to maximize coating porosity without sacrificing coating deposition efficiency. The resultant coatings have been assessed for their microstructure, adhesion strength, furnace cyclic lifetime, thermal conductivity and sintering behavior. Finally, the impact of spray processing on coating economics is discussed. The use of a Low-Density powder with a high-power plasma system allows a high-porosity coating to be manufactured more efficiently and more cost effectively than with conventional powder feedstock. The improvement in thermal properties for the experimental coating demonstrates there is scope to improve industrial coatings by designing with specific thermal resistance rather than thickness and porosity as coating requirements.

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