Electron mobility enhancement by electric field engineering of AlN/GaN/AlN quantum-well HEMTs on single-crystal AlN substrates

• Published in: Applied physics letters Vol. 124; no. 15
• Main Authors: Chen, Yu-Hsin, Encomendero, Jimy, Savant, Chandrashekhar, Protasenko, Vladimir, Xing, Huili (Grace), Jena, Debdeep
• Format: Journal Article
• Language: English
• Published: Melville American Institute of Physics 08.04.2024; American Institute of Physics (AIP)
• Subjects: Aluminum nitride; Density; Electric fields; Electron gas; Gallium nitrides; Heterostructures; High electron mobility transistors; High power microwaves; Interface roughness; Physics; Quantum wells; Room temperature; Scattering; Semiconductor devices; Single crystals; Substrates; Transport properties
• ISSN: 0003-6951; 1077-3118
• DOI: 10.1063/5.0190822

To enhance the electron mobility in quantum-well high-electron-mobility transistors (QW HEMTs), we investigate the transport properties in AlN/GaN/AlN heterostructures on Al-polar single-crystal AlN substrates. Theoretical modeling combined with experiment shows that interface roughness scattering due to high electric field in the quantum well limits mobility. Increasing the width of the quantum well to its relaxed form reduces the internal electric field and scattering, resulting in a binary QW HEMT with a high two-dimensional electron gas (2DEG) density of 3.68 × 10 13 cm–2, a mobility of 823 cm2/Vs, and a record-low room temperature (RT) sheet resistance of 206  Ω / □. Further reduction of the quantum well electric field yields a 2DEG density of 2.53 × 10 13 cm–2 and RT mobility > 1000 cm2/V s. These findings will enable future developments in high-voltage and high-power microwave applications on the ultrawide bandgap AlN substrate platform.