news digest compound semiconductor
rhombus4
Iron-arsenic compounds examined for
Highest power output for
quantum critical point - 11 Jan, 2010
638-nanometre
red LD - 14 Jan, 2010
The ability of electrons to conduct electricity materials, something which could prove
with no resistance is linked to their magnetic essential to the future development of Mitsubishi has revealed a 638-nanometre
properties, new research has revealed. semiconductors. wavelength red LD which could prove ideal
for the increase in popularity of pico
A recently-discovered class of iron-based The researchers noted that projectors. Mitsubishi has revealed a 638-
superconductors have undergone high-temperature superconductors could nanometre wavelength red LD which could
experiments by a team of Chinese and US be used toprogress MRI scanners, high- prove ideal for the increase in popularity of
physicists who discovered that electrons speed trains and electric generators. Mr Si pico projectors.
being able to conduct electricity with no stated: “The evidence from this study
resistance are linked to their magnetic bolsters the hypothesis that high- A 638-nanometre wavelength red laser
properties. temperature superconductivity in the iron diode (LDs) has been revealed and its
pnictides originates from electronic maker asserted that it offers the world’s
Rice University revealed in Physical Review magnetism.” highest power output for this band of LDs.
Letters that examination of several iron- Mitsubishi announced the launch of the
arsenide compounds found that the strength Low-temperature superconductivity is 638-nanometre LD, with a power output of
of the magnetic order was reduced when caused by ionic vibrations. 500 milliwatts that makes it ideal for devices
smaller phosphorus atoms replaced arsenic such as pico projectors and portable display
atoms. Last year, Ames Laboratory revealed that systems that need a red light source with
iron-arsenide semiconductors’ ability to high brightness.
Qimiao Si, a Rice physicist, said this carry current could hold potential for the
highlights evidence that a magnetic development of zero-resistance power The semiconductor industry could be
quantum critical point can be found in these transmission. interested in this development as pico
projectors are often embedded in or
connected to laptop computers and mobile
III-nitride LDs marked as potential replace for solid
telephones, with LDs and light emitting
diodes mainly used as the light source. LDs
state lasers - 8 Jan, 2010
deliver higher output power with less
consumption than LEDs, meaning the
efficiency of semiconductors may constantly
Solid state lasers are expensive to adopt on also make efficient and effective be addressed to ensure optimal
a wide scale for commercial applications replacements for gas or solid state lasers. performance.
and, as such, researchers have developed III-nitride based green LDs - unlike second-
the potential for AlGaN-cladding-free III- harmonic generation green LDs - have the Furthermore, LDs offer a wider range of
nitride LDs to be used as their replacement. potential for reduced manufacturing costs, colours compared to lamp-based projectors.
increased reliability and efficiency, Pico projectors require miniaturised
A team of researchers have demonstrated compactness and the promise of access to semiconductors as while sufficient storage
that electrically-driven indium gallium nitride a wider range of available wavelengths. is needed, it needs to fill as little space as
(InGAN)-based laser diodes (LDs) with an possible to accommodate an attached
aluminium gallium nitride (AIGaN)-cladding LDs are lasers where semiconductors are display screen.
free epitaxial structure can be grown on the active medium, similar to the qualities of
semipolar GaN substrates. light-emitting diodes. They are widely used
in telecommunications, as well as in better characteristic temperatures and more
The study published in Applied Physics barcode readers. stable properties than shorter ones.
Express revealed that a maximum The wavelength of green is seen as more
wavelength of 506.4 nanometres was While solid state lasers could serve many stable than other conventional diode
observed under pulsed operation, which applications, mass-produced diode lasers colours, such as blue and yellow, which is
could be of interest to the semiconductor cost less and therefore support mass- why the development of green LDs could be
industry as the wavelength is the longest market applications. so important to scientists.
reported for AIGaN-cladding-free III-nitride
LDs. Researchers for the Japan Society of However, rather than using the more Commenting on findings, the study report
Applied Physics wanted to build on the fact expensive solid state lasers, manufactures said: “The lasing wavelength was stable
that green LDs based on the alloys have could replace these with III-nitride based below 0.5 per cent duty cycle and thereafter
been touted as potential sources for next- green LDs. red-shifted with increasing duty cycles, due
generation display applications. to self-heating of the device. Lasing was
Longer wavelengths - as demonstrated in observed up to seven per cent duty cycle
Furthermore, it has been suggested by the this study - could prove beneficial to the with a maximum lasing wavelength of 506.4
semiconductor industry that the LDs could telecommunications industry as they have nanometres.”
20 www.compoundsemiconductor.net January/February 2010
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