GaN HEMTs Application Brief

SSTR-F shows that varying the thickness of undoped GaN layers above the buffer can significantly affect the device’s heat management ability.


In the realm of high-power electronics, High Electron Mobility Transistors (HEMTs) represent a significant advancement, particularly for applications demanding robust power handling capabilities like wireless communications and radar systems. However, as HEMTs made from materials such as gallium nitride (GaN) and aluminum gallium nitride (AlGaN) operate at elevated powers, they face challenges related to heat management. The efficient dissipation of heat is essential to maintain performance and prevent thermal failure.

The Problem

One of the primary obstacles in enhancing the performance of GaN/AlGaN HEMTs is the high cost and thermal mismatch of substrates used in their construction. Substrates such as silicon, silicon carbide, or sapphire, while cheaper, do not effectively match the thermal properties of GaN/AlGaN, leading to inefficient heat dissipation. Conversely, more suitable substrates like GaN or aluminum nitride are prohibitively expensive, making them less feasible for general use. This substrate challenge results in a trade-off between cost and performance, limiting the broader application of high-performance HEMTs.

The Solution

Laser Thermal has addressed this thermal management challenge by leveraging a tool called steady-state thermoreflectance in fiber optics (SSTR-F). This advanced technology allows for non-destructive, precise measurement of thermal properties within semiconductor layers.

By partnering with the Naval Research Laboratory and others, Laser Thermal evaluated the performance of GaN/AlGaN HEMTs grown on a new, cost-effective substrate developed by Qromis, Inc., known as QST™. The use of SSTR-F showed that varying the thickness of the undoped GaN layer above the buffer significantly affected the device’s ability to manage heat. Specifically, structures with a thicker 500-nm UID GaN layer displayed superior thermal conductivity and, consequently, cooler operation at high power outputs compared to those with thinner layers.

This breakthrough clearly shows the critical role of precise thermal analysis in optimizing semiconductor design for better performance and reliability.

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