GaN electronics technology
rhombus4
MicroGaN is
receiving over
€9 million of
funding from
the European
Commission
through a
seventh
framework
program
that has the
theme of
nanosciences,
nanotechnologies,
materials and
new production
technologies
the internal stresses in the GaN film. “Due to the stress, sensors.” The Bath team has designed a
the cantilever will bend downwards, and this can be 50 photolithographic mask and is now optimizing the
µm to 20 µm, depending on the structure,” says Heinle. geometry of these epitaxially grown cantilever and
One way to address this issue is to introduce double- membrane sensors. “Once the geometry is optimized, our
clamped structures that are better at coping with any collaborators in the MORGaN program will be able to
initial stresses in the material. design the most appropriate transducer. We are getting
close to that stage now.”
The University of Bath is developing a process for
producing nitride films on silicon substrates with Diamond platforms
incredibly low levels of stress. Their approach - pioneered A team of suppliers of high-performance, diamond-base
by the academic Wang Nang Wang - involves a substrates is underpinning much of the effort in the
nanoscale lateral overgrowth technique that begins with MORGaN project. Diamond promises to be a great
the formation of an array of nano-columns on a GaN foundation for these devices, thanks to its incredibly high
template. Adjusting the growth conditions can then lead thermal conductivity of typically 2000 Wm
-1
K
-1
. This
to the coalescence of the GaN nano-columns into a enables it to act as a very efficient heat spreader that
continuous planar film of a low-stress, high-quality rapidly sucks the heat away from the localized hot spots
semiconductor. within devices.
The Bath team is looking to extend this concept to the Providing funding for this aspect of the program might
growth of thin membranes of GaN clamped either at all raise a few eyebrows, because the epitaxial teams could
edges or along just one edge. In the latter configuration simply import the diamond composite wafers that are
the structure will resemble a microscopic cantilever grown under development by firms such as sp3 Diamond
out from the semiconductor surface. “When released Technologies and Group 4 Labs. However, the Element
these cantilevers will sense applied forces by the Six R&D Operations Manager Geoff Scarsbrook, who is
piezeoelectric effect as they bend,” explains Duncan heading-up this part of the MORGaN project, says that
Allsopp, a researcher at Bath University. “We have funding of diamond-based substrates is justifiable,
already demonstrated the growth of short, stubby because the technology is far from mature: “Whilst the
cantilevers and we are now extending our research to benefits of incorporating a diamond layer are well
clamped membrane structures to act as pressure understood, the optimum technology for integrating the
November / December 2009 www.compoundsemiconductor.net 29
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