While theoretically the ideal semiconductor, diamond has not yet become mainstream in transistors and other components.
Researchers have fabricated a diamond field-effect transistor (JFET) with a current conduction of 50 mA. According to this study published in
IEEE Electron Device Letters, this is five times higher than the previous record for a transistor with bulk conduction.
Most transistors are made of silicon, silicon carbide or gallium nitride. Diamond theoretically has better properties than all these materials, but it is difficult to dope to make it conductive and its artificial growth remains challenging to control. Diamond transistors have nevertheless been developed for about thirty years and their performance is improving.
Ultimately, such components would make excellent converters for electric vehicles and aeronautics. In most cases, diamond transistors only conduct current on their surface, not throughout their volume, which can pose limitations in terms of conductivity control, manufacturing reproducibility and reliability. Bulk conduction transistors offer better scalability instead of remaining as tiny prototypes, but their conductivity remains low and does not exceed ten milliamperes (mA).
Researchers from the
Néel Institute (CNRS), the Plasma and Energy Conversion Laboratory (
LAPLACE, CNRS/Toulouse INP/Univ. Toulouse) and the startup
DIAMFAB (France) have designed a diamond transistor achieving a record bulk current conduction of 50 mA.
The component is a field-effect transistor (JFET) using bulk conduction, models which consist of three terminals: the gate, drain and source. The team succeeded in obtaining homogeneous layers of diamond, here doped with boron, without introducing harmful defects. They were thus able to increase the useful volume of the transistor and its gate, which reaches 14.7 mm (0.58 inches) with 24 parallel fingers. The transistor is then no longer just a miniature demonstrator, but a fully usable component.
a) Cross-sectional diagram of the transistor, b) top view under optical microscope.
© Michez et al.
The scientists now plan to improve the design and fabrication of these transistors, particularly to develop their voltage withstand capability, i.e. their ability to block current on command. The next step will be to test their performance in environments closer to applications. Finally, the researchers will focus on another transistor architecture: metal-oxide-semiconductor field-effect transistors (MOSFETs).
References:
Over 50 mA Current in Interdigitated Diamond Field Effect Transistor.
Damien Michez, Juliette Letellier, Imane Hammas, Julien Pernot, Nicolas C. Rouger.
IEEE Electron Device Letters, vol. 45, no. 11, pp. 2058-2061, Nov. 2024.
https://doi.org/10.1109/LED.2024.3453504
Article available on open archives
Arxiv and
HAL