A terahertz transmitter developed at the Technical University (TU) of Darmstadt, Germany, has set a new frequency record, 1.111 THz, for microelectronic devices. The innovative device is also minuscule and operates at room temperature, which could lead to its paving the way for new applications in, for example, nondestructive testing or medical diagnostics.

As reported in the December 8, 2011 advanced online issue of Applied Physics Letters (DOI: 10.1063/1.3667191), a team of physicists and engineers led by Michael Feiginov at the TU Darmstadt’s Institute for Microwave Technology and Photonics developed a resonance tunnel diode (RTD) for generating terahertz electromagnetic radiation. The RTD terahertz transmitter occupies less than a square millimeter in area and can be produced using mostly conventional semiconductor-device fabrication technologies.

Terahertz transmitter; RTD stands for resonance tunnel diode. Image: Michael Feiginov/TU Darmstadt. Reproduced with permission from Appl. Phys. Lett. (2011), DOI: 10.1063/1.3667191. © 2011 American Institute of Physics.

The heart of their RTD is a dual-barrier structure, within which a quantum well (QW) is embedded. The QW is a very thin layer of indium-gallium arsenide semiconductor sandwiched between a pair of ultrathin barrier layers of aluminum-arsenide semiconductor. Each of these layers is one nanometer to a few nanometers thick. Due to a quantum-mechanical effect, this dual-barrier structure ensures 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, Germany, a fabricator of microelectronic circuit components, in producing their diode. Other authors of the article are C. Sydlo and P. Meissner of TU Darmstadt and O. Cojocari of TU Darmstadt and ACST GmbH.