Gallium nitride (GaN) has carved its place in the semiconductor world—the 2014 Nobel Prize in Physics acknowledged the efforts of the three physicists who succeeded in making high quality GaN crystals, a key component of powerful, energy efficient light-emitting diodes. Another area where the semiconductor made big impact is in Blu-ray storage devices. In addition to its significant role in today’s optoelectronics, GaN is also poised to drive next-gen power electronics devices.
“Power electronics is not the electronics that is most commonly visible like cellphones or computers. But practically in every device, be it a laptop, an AC, or an automobile, there are power electronic circuits that have to handle very high powers, currents and voltages. It is through these circuits that power is routed and this constitutes the field of power electronics,” explained Srinivasan Raghavan (popularly known as Vasu), Associate Professor at the Centre for Nano Science and Engineering (CeNSE), Indian Institute of Science, Bangalore.
GaN is the mainstay of Raghavan’s research. This wide gap semiconductor combines unique material and electronic properties. Hard and robust, it has roughly three times the bandgap of silicon, about ten times higher electrical breakdown characteristics and high carrier mobility. Consequently, GaN devices can operate at high temperatures, have high switching speeds and support high current density. This opens up the field for new and innovative applications based on GaN, allowing technology to go beyond what has been achieved with silicon. “For instance, India is headed in a large way for photovoltaic (PV) installations. Increasingly, this PV industry is moving towards mini and micro inverters. It is applications like these that may be enabled by GaN based devices, which are smaller because the material can handle higher power,” said Raghavan, citing one of many examples.
He has helped establish a semi-production scale growth facility that now consistently produces GaN-based transistors on Si wafers comparable with the best in the world. The material production is so consistent that CeNSE has now started providing these wafers to researchers all over the country. Efforts are on to build packaged discrete devices and systems around these structures. This will help create an entire ecosystem of GaN based electronics at IISc—from materials to devices to systems.
“The worldwide power electronics device market is 36 billion USD. And as power consumption goes up, the requirement for power electronics circuits will go up in a commensurate way,” said Raghavan. “And that is just the devices. The systems market is around 15 times the device market. So when you start working on GaN based materials, you are looking at a potential impact on a much larger power electronics market. What we have set up here in IISc is a GaN platform where many of these things can mushroom from,” he added.
Researchers at CeNSE have certainly made significant strides towards establishing a power electronics industry in the country based on GaN, thanks mainly due to the pioneering efforts of Raghavan. “We want India to have its rightful place in this segment,” said Rudra Pratap, Chairperson and Professor of CeNSE.
Raghavan’s contributions have been duly recognized—he is the first recipient of Prof. Ramakrishna Rao Chair, endowed by Centum Electronics Limited (a Bangalore based company). “It came as a surprise,” acknowledged Raghavan. “Of course the chair brings with it recognition of your services. It shows that society cares,” he said. Prof. Ramakrishna Rao, a former Professor of Instrumentation at IISc, in whose name the Chair has been instituted said, “Nanoscience is an advanced and relevant science. It is the science of the future. We should encourage researchers striving to achieve progress in this field.”
(Write up by Harini Barath. She is a science writer. She is currently the Program Manager for Science Communication at IndiaBioscience.)