Indigenous high-power microwave transistors

Image: Sagun Shekar

Most gallium nitride (GaN) microwave transistors are import-restricted because these are highly strategic in nature and are used in radars, jammers, electronic warfare and even telecom infrastructure. These transistors amplify or boost the radio waves when sent from the transmitter in most wireless communication or military applications.

Almost all such GaN transistors are realised on the rather expensive silicon carbide (SiC) platform; developing these devices on GaN on silicon platform is promising for economy of scale and volume. However, such an approach has its own set of challenges.

In new work, for the first time in India, researchers at the Centre for Nano Science and Engineering (CeNSE) have developed and demonstrated a fully indigenous GaN on silicon microwave transistor wherein the material stack or the wafer is grown at IISc, and the transistors are fully designed, fabricated and tested at IISc. The team has achieve a power of 8W at a frequency of 10 GHz, which is of strategic interest. For this, the atomic layer-by-layer deposition of the material stack was carefully studied and optimised and the know-how of fabrication of various unit process modules was developed.

The researchers engineered the energy landscape of the material-stack by tuning a fundamental property of GaN, called ‘polarisation’. This helped them get rid of intentional impurities such as carbon or iron that are otherwise mandatory to be added in such wafers to make them withstand high voltages.

For the first time, the team has demonstrated microwave power transistors based on GaN-on-silicon which do not contain any intentional carbon or iron impurities.

From left to right: Hareesh Chandrashekar, Roopa Jayaramaiah, Digbijoy Nath, Shonkho Shuvro, Aniruddhan Gowrisankar, Srinivasan Raghavan, Prosenjit Sen (Photo: Sagun Shekar)

REFERENCE:

Shuvro S, Gowrisankar A, Jayaramaiah R, Venugopalrao A, Chandrasekar H, Sen P, Muralidharan R, 8 W at 10 GHz in AlGaN/GaN High Electron Mobility Transistors on Silicon Without Any Carbon or Iron Doping, Physica Status Solidi RRL (2025)
https://onlinelibrary.wiley.com/doi/abs/10.1002/pssr.202400409

CONTACT:

Digbijoy Nath
Associate Professor
Centre for Nano Science and Engineering (CeNSE)
Indian Institute of Science (IISc)
Email: digbijoy@iisc.ac.in

Shonkho Shuvro
PhD student
Centre for Nano Science and Engineering (CeNSE)
Indian Institute of Science (IISc)
Email: shonkhos@iisc.ac.in

The work is funded by MeitY, MoE (MHRD) and DST. Initial part of the work was also funded by ISRO (SCL) and SERB IMPRINT-II.