LEDs ♦ news digest
Yap’s team had made a transistor without a semiconductor. When sufficient voltage was applied, it switched to a conducting state. When the voltage was low or turned off, it reverted to its natural state as an insulator.
What’s more, there was no “leakage”. In other words, no electrons from the gold dots escaped into the insulating BNNTs, thus keeping the tunnelling channel cool. In contrast, silicon is subject to leakage, which wastes energy in electronic devices and generates a lot of heat.
Other people have made transistors that exploit quantum tunnelling, explains Michigan Tech physicist John Jaszczak, who has developed the theoretical framework for Yap’s experimental research. However, those tunnelling devices have only worked in conditions that would discourage the typical cellphone user.
Jaszczak says, “They only operate at liquid-helium temperatures”.
The secret to Yap’s gold-and-nanotube device is its submicroscopic size: one micron long and about 20 nanometres wide.
”The gold islands have to be on the order of nanometres across to control the electrons at room temperature,” Jaszczak says. “If they are too big, too many electrons can flow.” In this case, smaller is truly better: “Working with nanotubes and quantum dots gets you to the scale you want for electronic devices.”
“Theoretically, these tunnelling channels can be miniaturised into virtually zero dimension when the distance between electrodes is reduced to a small fraction of a micron,” says Yap.
Yap has filed for a full international patent on the technology.
This work is described in the article “Room Temperature Tunneling Behavior of Boron Nitride Nanotubes Functionalized with Gold Quantum Dots,” by Chee Huei Lee et al, published online on June 17th in Advanced Materials. DOI: 10.1002/adma.201301339
This work was funded by the Office of Basic Energy Sciences of the US Department of Energy (Award # DE- FG02-06ER46294, PI:Y.K.Yap) and was conducted in part at ORNL (Projects CNMS2009-213 and CNMS2012- 083, PI: Y.K.Yap).
EPC’s 1 MHz eGaN FET buck converter board is 96% efficient
The firm believes its latest enhancment mode gallium nitride transistor demonstrates size reduction and efficiency enhancement for power conversion with high frequency switching
Efficient Power Conversion Corporation (EPC) has introduced the EPC9107, a fully functional buck power conversion demonstration circuit.
This board is a 9 V - 28 V input to 3.3 V, 15 A maximum output current, 1MHz buck converter.
It uses the EPC2015 eGaN FET in conjunction with the LM5113 100V half-bridge gate driver from Texas Instruments. The EPC9107 demonstrates the reduced size and performance capabilities of high switching frequency eGaN FETs when coupled with this dedicated eGaN driver.
The EPC9107 demonstration board is 3” square and contains a fully closed-loop buck converter with optimized control loop. The complete power stage including eGaN FETs, driver, inductor and input/output caps is in an ultra compact 0.5” x 0.5” layout to showcase the performance that can be achieved using the eGaN FETs with the LM5113 eGaN driver.
Despite its small size, the board has peak power efficiency greater than 96% and is capable of delivering 15 amps of current at 3.3 volts. To assist the design engineer, the EPC9107 demonstration board is easy to set up and contains various probe points to facilitate simple waveform measurement and efficiency calculation.
Raytheon GaN technology is ideal for defence applications
The firm has been awarded for its affordable and effective gallium nitride RF based technology
Raytheon was honoured by the Office of the Secretary of Defence (OSD) for successful completion of a Defence Production Act (DPA) Title III Gallium Nitride (GaN) production improvement program.
This culminated in more than a decade of government and Raytheon investment in GaN RF (radio frequency) circuit technology.
July 2013
www.compoundsemiconductor.net 153
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