Power Electronics ♦ news digest
(ADS) service report, “US DOD Budget Cuts will Place Emphasis on Advanced Electronics Capabilities,” predicts that this continued emphasis will translate into an upwards defence sector semiconductor market growth trajectory over 2010 - 2015 with a CAGR (compound annual growth rate) of over 6 %.
These efficiency decisions are designed to save the Department of Defence more than $150 billion over the next five years primarily by reducing overhead costs, improving business practices and culling excess or troubled programs.
Most of the resulting savings will be used by the Army, Navy, Marine Corps and Air Force to invest in high priority programs that strengthen warfare capability.
“Despite defence budget growth dwindling to zero by 2015, there is recognition that the mistakes of the past should not be repeated by making drastic cuts to the overall defence budget,” stated Asif Anwar, ADS Service Director. “Progress made by China and Russia will require that the US continue its focus on technology”.
“Investment in high priority programs that strengthen fighting capability will translate into continued development on radar, EW, communications and other advanced defence issues,” noted Eric Higham, ADS Service Director North America. “Strategy Analytics believes that this will maintain demand for semiconductors with a particular emphasis on technologies such as GaAs, GaN and SiGe (Silicon Germanium).”
optoelectronics and sensors.
Both materials are also used in more complex devices such as resonators and, more recently, in nanogenerators that convert mechanical energy from the environment (body movements, for example) to power electronic devices.
The latter application relies on the fact that GaN and ZnO are also piezoelectric materials, meaning that they produce electric charges as they are deformed.
In the past few years, nanostructures made of these materials have shown a plethora of potential functionalities, ranging from single-nanowire lasers and LEDs.
In a recent publication, Horacio Espinosa and Ravi Agrawal of Northwestern University based in Illinois, have reported that piezoelectricity in GaN and ZnO nanowires is in fact enhanced by as much as two orders of magnitude as the diameter of the nanowires is decreased
This finding is very exciting because it suggests that constructing nanogenerators, sensors and other devices from smaller nanowires will greatly improve their output and sensitivity,” Espinosa said.
GaN Nanowires are the Giants of Piezoelectricity
The piezoelectric coefficient in 2.4 nm diameter GaN nanowires is about 100 times larger when compared to the coefficients of the material on a macroscale.
GaN and ZnO are two of the most technologically relevant semiconducting materials in optoelectronics today. GaN is ubiquitous in blue lasers and LEDs whilst ZnO is used in
“We used a computational method called Density Functional Theory (DFT) to model GaN and ZnO nanowires of diameters ranging from 0.6 nm to 2.4 nm,” added Agrawal. The computational method is able to predict the electronic distribution of the nanowires as they are deformed and thus allows calculation of their piezoelectric coefficients.
The researchers’ results show that the piezoelectric coefficient in 2.4 nm diameter nanowires is about 20 times larger and about 100 times larger for ZnO and GaN nanowires, respectively, when compared to the coefficient of the materials at the macroscale. This confirms previous computational findings on ZnO nanostructures that showed a similar increase in piezoelectric properties.
January / February 2011
www.compoundsemiconductor.net 151
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