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Novel Millimetre And Terahertz Wave Photodetectors

Photodetectors sense light and other electromagnetic energy, and are used in a wide range of technology. Long- wavelength photodetectors, especially those that operate in the millimetre and terahertz wave ranges, in particular, have many applications in many fields.

Now, scientists at Nanyang Technological University’s School of Electrical and Electronic Engineering (EEE), Professor Zhang Dao Hua and his team members Dr Tong Jinchao and Dr Xu Zhengji, together with Professor Huang Zhiming and his team members Dr Zhou Wei and Qu Yue at Shanghai Institute of Technical Physics, Chinese Academy of Science, have invented new long- wavelength photon detectors. Their creation could be used to improve technologies in many other fields, especially in security checking technologies. In addition to filing a patent, the related work has been published in Nature Communications (NatureCom 8, Article number: 1660, 2017).

Long-wavelength photodetectors that are now commercially available include Golay cells, pyroelectric elements, bolometers and Schottky barrier diodes.

The first three, however, suffer from a slow response or require cryogenic cooling if they are used in thermal- sensing applications.

Meanwhile, the diodes, which are widely used in radio-frequency and microwave ranges, are high-speed but require advanced fabrication and material growth techniques.

The EEE scientists developed an antenna-assisted sub-wavelength ohmic metal-semiconductor-metal structure, made of gold and indium antimonide (InSb), that can detect photons in the millimetre and terahertz wave ranges.

Under transverse magnetic polarised illumination, the gold planar dipole antenna efficiently couples photons into the structure. Localised surface plasmon polaritons (SPPs) are excited by the coupled photons within the InSb semiconductor, especially near the semiconductor-metal interfaces on the top facet.


The EEE invention worked successfully in simulations and experiments. The scientists also achieved a noise equivalent power of 1.5 × 10-13 W Hz−1/2 with a device with a spacing of 10 micrometres under a DC bias current of 3.5 mA for a beam of 0.151 meV photons at room temperature.

By Professor Zhang Dao Hua
Click here to find out more.

Published on 9 Oct 2018​
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