news digest ♦ Power Electronics
Few-layer graphene films preserve their excellent thermal properties even when their thickness is only a few nanometres, which is unlike metal or semiconductor films. The latter makes them excellent candidates for applications as the lateral heat spreaders and interconnects. The Balandin group researchers designed and built graphene- graphite “quilts” on top of GaN transistors. The graphene-graphite quilts’ function was to remove and spread the heat from the hot spots – the opposite of what you expect from the conventional quilts.
quality control of graphene and demonstration of the first selective gas sensor implemented with pristine graphene. The work on thermal management of GaN transistors with graphene quilts was supported by the Office of Naval Research. Balandin’s research of the thermal properties of graphene was funded by the Semiconductor Research Corporation and the Defence Advanced Research Project Agency.
Say hello to millimetre wave GaN PAs
Millitech’s gallium nitride power amplifiers offer wideband power covering 75 GHz to 102 GHz Millitech is touting its next generation E-Band and W-Band compact and high power solid state power amplifiers.
From left to right: Guanxiong Liu, Alexander Balandin and Zhong Yan, who worked on the project
Using micro-Raman spectroscopic thermometry the researchers demonstrated that temperature of the hot spots can be lowered by as much 20 degrees Celsius in transistors operating at the large power levels.
Millitech GaN Power Amplifier
The GaN based power amplifiers represent a quantum leap in output power at E-Band and W-Band with up to 3 W of output power and up to 20% PAE available in standard models.
From left, cross-sectional schematic of the GaN HFET with graphene quilt for heat spreading; current-voltage characteristics of GaN HFET with and without graphene-based heat spreaders demonstrating improvement in the saturation current due to lower junction temperature in the device with graphene quilt
The computer simulations performed by the group suggested that graphene quilts can perform even better in GaN devices on more thermally resistive substrates. The Balandin group is also known in graphene community for their investigation of low-frequency noise in graphene transistors, development of the first large-area method for
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www.compoundsemiconductor.net June 2012
The new AMP models offer catered performance over specific allocated bands or wideband power covering 75 GHz to 102 GHz. The E-Band (WR-12) models cover the commercially allocated 71-76GHz and 81-86 GHz bands.
The W-band models cover 75-102 GHz Each amplifier has internal bias circuitry that generates gate control voltages, provides proper voltage sequencing and incorporates reverse voltage protection from a single positive external bias. Single device models are available with nearly 1W of saturated output power. Standard models also include 2-way and 4-way Solid State Power Amplifiers with up to 3W of saturated output power.
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