Materials for electronics that operate in harsh environments
Electronic devices and sensors often need to be used in high temperatures, high electric fields or in highly corrosive environments. The EU-funded MORGAN (Materials for robust gallium nitride) project investigated how diamond and gallium nitride (GaN) heterostructures can be used to produce the best materials for such conditions. Project partners developed innovative diamond-based composite substrates, and carried out the first European demonstration of 2-inch wafers. They studied the direct growth of GaN on single crystal and polycrystal diamond. 2D electron gas confinements were mastered on both types of crystalline diamond structures. The MORGAN team developed GaN growth on a variety of substrates such as sapphire, silicon carbide, silicon and composite, using specific compliant layers and nucleation schemes or interlayer to accommodate crystalline and thermal expansion mismatches. The first high-electron-mobility transistor (HEMT) obtained by direct growth of a GaN heterostructure on single crystal diamond was demonstrated. It exhibited microwave operation with cut-off frequencies in the 40 GHz range. Scientists realised indium aluminium nitride/GaN HEMT growths on diamond-based composite substrates. They also developed high-temperature-pressure and electrochemical sensors together with their associated packaging. Sensors working up to 80 bar were demonstrated and testing temperatures up to 450 °C were used. In addition, excellent electrochemical sensors with fast reaction times were demonstrated. A robust packaging process based on ceramics and silver interconnects was developed and successfully temperature-cycled to 650 °C. MORGAN also successfully demonstrated efficient 3D heat exchangers using copper based on inkjet technology. Dissemination mainly included 27 articles and over 175 presentations at major events. By combining diamond and GaN, MORGAN showed how these two materials can be exploited to produce the best materials and devices for ultimate performance in extreme environments, particularly in high temperatures and high electric fields.
Keywords
Electronic devices, sensors, MORGAN, gallium nitride, diamond
