Applications of a new semiconductor device

The transistor, a semiconductor device used to boost or switch electronic signals, is a widely used component in almost every electronic device, big and small. In fact, it is often considered as one of the greatest inventions of the 20th century. As electronic devices become sophisticated and find new applications, different types of transistors are being designed and developed to suit those applications. Among them is the bipolar junction transistor (BJT), a transistor that uses both electron and hole charge carriers (bipolar) for its operation. It is now touted to play a big role in the Internet of Things (IoT) applications.

But how does this transistor fit in the bigger landscape? Almost every IoT solution needs sensors, which collect data from their surroundings. This data (or signals) could either be digital like the images captured by a camera, or analogue as in the case of audio signals.

Processing the two types of signals needs a versatile technology platform that can work with mixed signals and result in optimal performance. While the Complementary Metal Oxide Semiconductor (CMOS) transistors handle digital signals, BJTs work with analogue signals. Bi-CMOS (short
for Bipolar-CMOS) technology combines the two transistor technologies in one chip.

In space and communication-related applications, BJTs are used in antennas for communications since they can work with very high-frequency signals. Conventionally, gallium arsenide (GaAs) or gallium nitride (GaN) based transistors are used in such antennas which are stand-alone and result in bulkier chips.

Now, researchers at the Indian Institute of Technology, Bombay (IIT-B), in a collaborative effort with ISRO’s Semi-Conductor Laboratory (SCL), Chandigarh, have developed a completely indigenous BJT that can work with Bi-CMOS. This development was the result of a year-long research led by Professor Udayan Ganguly and Dr Piyush Bhatt.

“The technology adds high-frequency circuits to the existing digital CMOS technology. It enables high-frequency communications and analogue or mixed chips for various applications like IoT and space,” says Udayan, who is also the co-principal investigator at the Centre of Excellence in Nanoelectronics (CEN) at IIT-B. “Bi-CMOS technology with integrated BJT based amplifiers reduces form factor, power consumption and cost — all essential for space applications,” he adds.

Indigenous technology

India has two semiconductor manufacturing organisations — STAR-C (a unit of SITAR by Government of India) and the Semi-Conductor Laboratory, producing high frequency, low power digital CMOS for strategic and national needs. However, international tech giants have largely pioneered cutting-edge semiconductor technologies.

These exclusive technologies may be availed through technology transfers — the process of transferring scientific findings from one organisation to another for the purpose of further development and commercialisation.

“To have unfettered access to such technologies for national needs, indigenous technology development is a must,” remarks Udayan, citing the reasons for the need to augment this production technology indigenously. He also points out two important gaps that have stymied indigenous technology development — the gap in CMOS technology development and manufacturing expertise, and the gap in advanced semiconductor manufacturing.

“While electronics is one of the top research-intensive areas globally, India has not had a significant stake until the Centres for Excellence in Nanoelectronics (CENs) were seeded at IIT-B and IISc, Bengaluru by the Ministry of Electronics,” he says.

Pointing out the need for fabrication facilities, Udayan adds, “While the electronics policy of 2017 claims that electronics imports will outstrip oil imports by 2020, the mega-fab creation in India is still under work.” In this context, the development of the indigenous BJT is indeed a milestone for the CEN at IIT-B.

The technology can not only provide strategic applications in the areas of space and defence but also in the development of digital and analogue chips. Going forward, these chips can be developed and manufactured by SCL or can be expanded for other corporate players to enter the business, leveraging Semi-Conductor Laboratory’s capabilities as a pilot line for scale-up.

“CEN has enabled the group to have excellent in-house ‘hands-on’ expertise in new technology development. In addition, the group has worked with various international research and manufacturing houses to develop key technologies,” says Udayan. He further adds that “every bit of knowledge, technique and idea in our research labs can translate into either a commercial or strategic product of the future.”

(The author is with Gubbi Labs, a Bengaluru-based research collective)