OBJECTIVE: To develop aluminum nitride-based platform for monolithic microwave integrated circuits for extreme radio frequency and high-power operation.
DESCRIPTION: The next generation of devices and systems for electronic microwave applications need to offer high frequencies, high power, compactness, high-performance, and high temperature operation. Several materials platforms such as silicon carbide (SiC), gallium arsenide (GaAs), silicon (Si), and aluminum nitride (AlN) are competing for market share in this emerging high frequency applications. Among them however, AlN stands out as an exceptional material for next-generation monolithic microwave integrated circuits (MMICs), offering a multitude of advantages that are paramount for advanced electronic systems. These include its ultrawide and direct bandgap (6.2 eV), large critical electric field (15 MV/cm) and high thermal conductivity (∼340 W/mK) allowing for efficient heat dissipation, critical in maintaining high power operation and reliability of high-frequency circuits. Current research and development focus is being placed on gallium nitride (GaN) and aluminum gallium nitride (AlGaN) high electron mobility transistors (HEMTs) for operations requiring both high-power and high frequency. This has led to demonstration of the state-of-the-art GaN HEMTs with output power of up to 8.84 W/mm at up to 94 GHz. However, the GaN HEMTs were fabricated on SiC substrates. AlN's compatibility with GaN and AlGaN HEMTs facilitates seamless integration, avoiding the lattice mismatch issues encountered in SiC substrates. This would enable the development of compact, high-frequency devices with superior operational capabilities. Additionally, current availability of insulating AlN of high substrate quality and large enough size ensures precise and reliable MMIC fabrication, and unwanted electrical interactions, thus, enhancing signal integrity at high frequencies. However, despite these advantages, research and development of AlN-based MMICs are still in their infancy and more effort is needed to fully harness its capabilities. The utilization of high-purity semi-insulating AlN as a substrate for MMICs requires precise knowledge of materials properties of AlN at millimeter-wave frequencies (such as electrical permittivities) to accurately predict the propagation delay and attenuation of waves along the transmission lines.
Speakers: Tom Oder
29 сен 2024
