The innovative transmitter, which was developed by scientists of TU Darmstadt, has set a new frequency record, 1.111 THz, for microelectronic devices. Image: Michael Feiginov / TU Darmstadt |
A
terahertz transmitter developed at the TU Darmstadt has generated the
highest frequency ever attained by a microelectronic device. The
innovative device is also minuscule and operates at room temperature,
which could lead to it paving the way for new applications in, e.g.,
nondestructive testing or medical diagnostics.
Although
terahertz (THz) electromagnetic radiation, which has wavelengths
ranging from 0.1 mm to 1 mm, penetrates common materials, such as
plastics, paper, fabrics, or ceramics, allows, e.g., nondestructively
testing workpieces, analyzing processes occurring in engine combustion
chambers while engines are running, inspecting packages and letters for
hazardous biological substances without need for opening them, it has
yet to establish a reputation for itself in scientific and engineering
fields. One of the hindrances involved was that, until now, transmitters
and receivers operating at THz frequencies were bulky and very
expensive.
However,
that situation might soon be reversed, since a team of physicists and
engineers led by Dr. Michael Feiginov at the TU Darmstadt’s Institute
for Microwave Technology and Photonics has developed a resonance tunnel
diode (RTD) for generating terahertz electromagnnetic radiation that
takes up less than a square millimeter and may be produced using more or
less conventional semiconductor-device fabrication technologies.
Furthermore, their innovative transmitter has set a new frequency
record, 1.111 THz, for microelectronic devices.
Feiginov, a physicist, noted, that, “That is the highest frequency ever generated by an active semiconductor device.”
He
was also able to theoretically prove that a minuscule transmitter, like
that developed by his group, should be capable of generating much
higher frequencies extending up to 3 THz. As Feiginov, who intends to
continue pursuing development work on the transmitter over the coming
years until generation of such higher frequencies has been achieved,
went on to say, “That was formerly regarded as impossible by those
involved in terahertz research.”
Achieving
such higher frequencies would allow attaining better spatial
resolutions, i.e., recognizing finer details, employing terahertz
electromagnetic radiation in materials testing and analysis than would
be possible at lower frequencies.
That
the RTD his group has developed operates at room temperature makes it
even more attractive for use in engineering applications. He further
commented that, “It might, for example, be utilized in spectroscopic
analyses of molecules that have transitions falling within the THz
range.”
According
to Feiginov, that would mean that substances that have thus far escaped
spectroscopic analysis in the THz range could be investigated employing
that widely practiced, scientific method, which would be of great
benefit in various fields, among them medicine, where it might, e.g.,
allow distinguishing diseased body tissues from healthy body tissues in
vivo.
Since
active semiconductor devices, such as the THz transmitter developed by
the TU Darmstadt group, represent the heart of modern informatics and
telecommunications technologies, as well as all sorts of electronic
equipment, Feiginov presumes that the device developed by his group will
prove useful in many other application areas that cannot readily be
foreseen at this stage.
“Extracting
higher frequencies from the device would lead to new applications, or
application areas, in the fields of computers, mobile telephones, and
other types of electronic equipment,” he said.
In
the course of miniaturizing their new device, the group of TU Darmstadt
researchers spent the past few years taking microelectronics close to
the limits of the technically feasible. The heart of their RTD is a
dual-barrier structure, within which a quantum well (QW) is embedded. A
QW is a very thin layer of indium-gallium arsenide semiconductor
sandwiched between a pair of ultrathin barrier layers of
aluminum-arsenide semiconductor. Every one of those layers is just one
nanometer to a few nanometers thin. This dual-barrier structure, plus a
quantum-mechanical effect, provides that electromagnetic waves generated
within a terahertz oscillator will be repeatedly amplified, rather than
attenuated, which means that the oscillator will emit continuous-wave
electromagnetic radiation at terahertz frequencies.
The
group of TU Darmstadt researchers collaborated with ACST GmbH, a local
fabricator of microelectronic circuit components, in producing their
diode.
Resonant-tunnelling-diode oscillators operating at frequencies above 1.1?THz
