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In the exploration of extreme high-temperature environments, Gallium Nitride (GaN), with its exceptional thermal stability and electronic performance, has emerged as a strong contender to succeed silicon materials.
Recent research, a collaboration between MIT and multiple institutions, has confirmed that even under extreme conditions of up to 500 degrees Celsius, GaN and its ohmic contacts can maintain structural stability, bringing new hope for high-temperature applications, including missions to the surface of Venus.
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A Key Material for Venus Exploration
The surface temperature of Venus can reach 480 degrees Celsius, hot enough to melt lead, rendering traditional silicon-based electronic devices unable to operate for extended periods. This has become a significant bottleneck hindering long-term lander missions to Venus. However, the emergence of gallium nitride is gradually changing this situation. While GaN is already widely used in phone chargers and communication equipment, the scientific community’s understanding of its performance in conditions exceeding 300 degrees Celsius remains limited.
Research Reveals GaN’s High-Temperature Potential
In a study published in Applied Physics Letters, the MIT research team conducted an in-depth analysis of the temperature dependence of ohmic contacts in gallium nitride devices. Ohmic contacts, as crucial components connecting semiconductors to external circuits, are vital for the overall device reliability.
The researchers surprisingly found that the GaN devices continued to operate at 500 degrees Celsius for 48 hours without significant degradation of the contact structures, demonstrating excellent thermal stability. This result greatly enhances its application potential in extreme environments such as the surface of Venus.
※Knowledge Supplement: An Ohmic contact is formed when a metal and a semiconductor are in contact, and the current and voltage between them exhibit a linear and symmetrical relationship. If the current-voltage relationship is non-linear, it is called a Schottky contact.
Improved Resistive Behavior and Contact Technology
The performance of semiconductor devices is often limited by contact resistance, which becomes particularly pronounced as device dimensions shrink. Traditionally, contact resistance at room temperature is relatively well understood, but its behavior at high temperatures remains an unknown area.
The MIT team employed two mainstream methods to enhance ohmic contacts:
- Depositing metal on gallium nitride and performing high-temperature annealing.
- Removing bulk gallium nitride and then regrowing highly doped gallium nitride to improve electron conduction efficiency.
The latter, led by Ohio State University, has been proven effective at room temperature, and this research is the first to verify its stable performance at high temperatures as well.
Advanced Testing and Long-Term Stability Verification
To comprehensively understand the material’s performance, the researchers built devices called “transmission line method structures” at MIT.nano and conducted short-term and long-term tests.
Short-term tests: Led by Professor Zhao at Rice University, the devices were placed on a hot chuck and rapidly heated to 500 degrees Celsius to observe real-time resistance changes.
Long-term tests: Conducted in a custom furnace previously developed at MIT, continuously monitoring for up to 72 hours.
The research results showed that the contact resistance remained stable within 48 hours, with performance similar to that at room temperature. Although signs of degradation began to appear after 48 hours, the researchers are working on strategies such as adding protective insulation layers to extend the material’s lifespan and improve stability.
Future of Microelectronics and Application Prospects
The findings of this research lay a solid foundation for developing high-temperature gallium nitride transistors capable of operating for extended periods on the surface of Venus.
In the future, these technologies will not only be applicable to planetary exploration but will also be widely used in extreme environments on Earth, such as geothermal energy development and jet engine monitoring.
John Niroula, an EECS graduate student at MIT and the first author of the paper, stated, “We are not in a rush to directly manufacture gallium nitride transistors but are starting from the fundamental level, gradually building an understanding of the behavior of materials and contacts at high temperatures, thereby advancing the design and development of overall electronic systems.”
This research demonstrates the importance of integrated research from the material level to the system level, foreshadowing a new era for the application of microelectronic technology in high-temperature environments.
Reference
- Capable of Withstanding Nearly 500°C High Temperatures on Venus, Gallium Nitride Electronics Enhance Space Exploration Capabilities
- Electronics That Defy Venus’ Heat: How Gallium Nitride Could Revolutionize Space Exploration
- John Niroula, Qingyun Xie, Nitul S. Rajput, …, Tomás Palacios (2024). High temperature stability of regrown and alloyed Ohmic contacts to AlGaN/GaN heterostructure up to 500 °C, Applied Physics Letters, Volume 124, Issue 20. DOI: 10.1063/5.0191297.
(Source of the first picture: AI generated)
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