Logic circuits equipped with diamond-based transistors

Tuesday, 08 August, 2017


Researchers from Japan’s National Institute for Materials Science (NIMS) have succeeded in developing logic circuits equipped with diamond-based MOSFETs at two different operation modes. Said to be a world first, their achievement is a step towards the development of diamond-integrated circuits operational under extreme environments.

Diamond has high carrier mobility, a high breakdown electric field and high thermal conductivity. It is therefore a promising material to be used in the development of current switches and integrated circuits that are required to operate stably at high temperature, high frequency and high power. However, it had been difficult to enable diamond-based MOSFETs to control the polarity of the threshold voltage and to fabricate MOSFETs of two different modes ― a depletion mode (D-mode) and an enhancement mode (E-mode) ― on the same substrate.

The Japanese researchers successfully developed a logic circuit equipped with both D- and E-mode diamond MOSFETs after making a breakthrough by fabricating them on the same substrate using a threshold control technique they had developed. Their work has been published in the journal IEEE Electron Device Letters.

Back in 2012, the research group identified the electronic structure in the interface between various oxides and hydrogenated diamond using photoelectron spectroscopy. One year later, the group succeeded in developing a diamond MOS capacitor with very low leakage current density and an E-mode hydrogenated diamond-based MOSFET.

In 2014, the group prototyped logic circuits by combining diamond-based MOSFETs with load resistors. Finally, in 2015, the group developed techniques to control D- and E-mode characteristics of diamond-based MOSFETs and identified the control mechanism.

The logic circuits with diamond-based transistors are believed to be promising devices for the development of digital integrated circuits that are required to stably operate under extreme environments, such as high temperature, as well as exposure to radiation and cosmic rays.

Image credit: Micrograph of a fabricated logic circuit equipped with diamond-based transistors.

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