In the realm of energy and electronics, understanding and optimizing the flow of current in transistors is crucial for improving the efficiency and performance of devices. A team of researchers from the Indian Institute of Science, TIFR Hyderabad, and the National Institute for Materials Science in Japan has made strides in this area by developing a novel technique for imaging current flow in diamond field effect transistors (FETs).
The researchers, led by Anuj Bathla and Kasturi Saha, have demonstrated a method called widefield quantum diamond microscopy. This technique uses nitrogen vacancy (NV) centers in diamond to noninvasively image the magnetic fields generated by current flow, providing micrometer-scale spatial resolution. The FETs in question are made of hydrogen-terminated diamond, which induces a two-dimensional hole gas (2DHG) at the surface, allowing current to flow.
The team electrically characterized the FETs under various drain-source biases and gate voltages, then used widefield NV magnetometry to image the current flow during operation. The magnetic field maps and reconstructed current density distributions revealed how current is injected at the source-drain contacts and transported beneath the hexagonal boron nitride (hBN) gated channel. Notably, the images showed variations in current density in the channel region due to non-uniformities or defects in the gate dielectric.
One interesting finding was the enhancement of the drain current (by approximately 600-900 microamperes) and a shift in the apparent threshold voltage during laser illumination. This observation suggests that laser light can induce changes in the channel’s electrostatics, affecting the flow of current. By correlating the gate-dependent magnetic images with simultaneous electrical measurements, the researchers gained new insights into buried interface transport and non-uniform gating effects in the transistor channel.
This research, published in the journal Applied Physics Letters, highlights the potential of widefield NV magnetometry as a powerful tool for probing charge transport in transistors and Van der Waals dielectric heterostructures. The technique is compatible with top-gated FETs, making it useful for mapping channel current distributions in emerging channel materials, such as 2D materials and wide bandgap channels. In the energy sector, this could lead to more efficient power electronics and improved understanding of materials for energy storage and conversion devices.
The practical applications of this research extend to the development of more efficient and reliable electronic devices, which are integral to various energy systems, from power grids to renewable energy technologies. By providing a clearer picture of current flow in transistors, this technique could help engineers design better devices and optimize their performance, ultimately contributing to a more sustainable energy future.
This article is based on research available at arXiv.