Key Takeaways & Executive Findings
- •• AlScN exhibits exceptional piezoelectricity with d33 increasing from 5 to 30 pC/N and electromechanical coupling coefficient (Kt2) rising from 7% to 25% at 40% Sc doping. • AlScN demonstrates ferroelectricity with remnant polarization exceeding 100 μC/cm2, surpassing conventional AlN limitations. • Micro/nano fabrication advances enable low-stress (<200 MPa) high-quality AlScN films and high-aspect-ratio structures for high-frequency devices beyond 10 GHz. • AlScN's multifunctional properties (piezoelectric, pyroelectric, ferroelectric) enable diverse applications in MEMS, RF communications, energy conversion, optoelectronics, and sensors.
Abstract
Aluminum scandium nitride (AlScN), an emerging Ⅲ-nitride semiconductor material, has attracted significant attention in recent years due to its exceptional piezoelectric properties, high thermal stability, tunable bandgap, and excellent compatibility with micro/nano fabrication. This paper systematically reviews the crystal structure, fundamental properties, and property modulation mechanisms of AlScN. It also summarizes recent progress in micro/nano fabrication technologies, including deposition, etching, and device integration. Furthermore, the applications of AlScN in diverse fields such as micro-electromechanical systems (MEMS), RF communications, energy conversion, optoelectronics and sensors are discussed. Finally, current challenges and promising future research directions for AlScN are outlined.
1. Introduction
Aluminum scandium nitride (AlScN), an emerging Ⅲ-nitride semiconductor material, has gained significant attention in microelectronics and optoelectronics owing to its exceptional piezoelectricity, high thermal stability, tunable bandgap, and compatibility with micro/nano fabrication[1−3]. As a derivative of AlN, AlScN enables precise control over crystal structure and functional properties through substitution of Al atoms with Sc. The resultant lattice distortion induces a disproportionate expansion of the c-axis lattice constant, thereby substantially enhancing spontaneous polarization and piezoelectric response. Studies demonstrate that with Sc doping concentration reaching 40%, the piezoelectric coefficient d33 of AlScN increases from 5 to 30 pC/N, while the electromechanical coupling coefficient (Kt2) rises from 7% to 25%[4, 5]. Remarkably, AlScN also exhibits ferroelectricity with remnant polarization (Pr) exceeding 100 μC/cm2, surpassing the functional limitations of conventional AlN. Furthermore, it inherits advantages including a wide bandgap (up to 6.2 eV), high thermal conductivity (~140 W/(m·K)), and high breakdown voltage (>10 MV/cm), which collectively enable its multiple applications[6−8].
Researchers optimize AlScN properties through multidimensional strategies: (ⅰ) compositional engineering: precise control of Sc doping concentration (20%−40%) to balance piezoelectric performance and structural stability, employing co-doping techniques (e.g., Sc−Mg, Sc−Yb)[9] to suppress phase separation at high Sc concentrations; (ⅱ) process optimization: adjusting substrate bias, temperature gradients, and gas flow rates during magnetron sputtering to achieve low-stress (<500 MPa), highly oriented thin films with full-width at half-maximum (FWHM) below 1.5°[10, 11]; (ⅲ) interface design: constructing AlScN/GaN or AlScN/SiC heterojunctions to improve interfacial carrier mobility through stress-compensation effects[12, 13].
The micro/nano fabrication of AlScN has garnered significant attention for its critical role in enabling miniaturized, high-performance devices. In thin-film deposition, breakthroughs by Clement et al.[14] achieved low-stress (<200 MPa) growth of high-Sc-ratio (20%−40%) AlScN films while maintaining wurtzite structural stability through optimized magnetron sputtering parameters (substrate temperature, sputtering power, and gas ratios). Additionally, Shao et al.[15] utilized co-sputtering with In-situ annealing to prepare AlScN films on 8-inch silicon substrates, demonstrating thickness nonuniformity below ±3% and enabling large-scale integration. For pattern processing, dry etching techniques have realized high-aspect-ratio (over 10 : 1) structures in AlScN, meeting the requirements for high-frequency acoustic wave devices for precision trenches. Further advances integrate nanoimprint lithography and electron beam lithography to scale AlScN-based MEMS features to submicron dimensions (e.g., 100 nm-linewidth electrodes), significantly boosting frequencies beyond 10 GHz[16].
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Shihang Liu, Jinfeng Gao, Jiajie Pan, Lin Li, Hanxiang Jia, Shuangzan Lu, Maowei Zhang, Bo Zhao, Jun Liu (2025). AlScN: characteristics, micro/nano fabrication and multiple applications. SinoTechIntel Verified Research. https://doi.org/10.1088/1674-4926/25060031
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Frequently Asked Questions
What is AlScN and why is it important?
AlScN (Aluminum Scandium Nitride) is an emerging III-nitride semiconductor with exceptional piezoelectric properties, high thermal stability, tunable bandgap, and compatibility with micro/nano fabrication. It is important for advanced applications in MEMS, RF communications, energy conversion, optoelectronics, and sensors.
How does Sc doping affect AlScN properties?
Sc doping in AlScN enhances piezoelectric response significantly. For example, at 40% Sc concentration, the piezoelectric coefficient d33 increases from 5 to 30 pC/N, and the electromechanical coupling coefficient (Kt2) rises from 7% to 25%. It also induces ferroelectricity with remnant polarization exceeding 100 μC/cm2.
What are the key fabrication techniques for AlScN?
Key fabrication techniques include magnetron sputtering for low-stress, highly oriented thin films, co-sputtering with in-situ annealing for large-scale integration, and dry etching for high-aspect-ratio structures. Advanced lithography methods like nanoimprint and electron beam lithography enable submicron features for high-frequency devices.
What are the main applications of AlScN?
AlScN is used in micro-electromechanical systems (MEMS), RF communications (e.g., high-frequency acoustic wave devices), energy conversion, optoelectronics, and sensors, leveraging its piezoelectric, pyroelectric, and ferroelectric properties.
What are the current challenges and future directions for AlScN?
Challenges include suppressing phase separation at high Sc concentrations and achieving precise control over film stress and orientation. Future directions involve co-doping strategies, interface engineering, and scaling up fabrication for commercial applications.
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