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Electronic transport in degenerate (100) scandium nitride thin films on magnesium oxide substrates
摘要： Scandium nitride (ScN) is a degenerate n-type semiconductor with very high carrier concentrations, low resistivity, and carrier mobilities comparable to those of transparent conducting oxides such as zinc oxide. Because of its small lattice mismatch to gallium nitride (GaN), <1%, ScN is considered a very promising material for future GaN based electronics. Impurities are the source of the degeneracy. Yet, which specific impurities are the cause has remained in contention. ScN thin films of various thicknesses were grown on magnesium oxide substrates in a (001) orientation using reactive magnetron sputtering across a range of deposition conditions. X-ray diffraction was used to verify crystal orientation. Film thicknesses ranging from 39 to 85 nm were measured using scanning electron microscopy. The electronic transport properties of the films were characterized using Hall-effect measurements at temperatures ranging from 10 to 320 K. At 10 K, the electron concentration varies from 4.4 (cid:2) 1020 to 1.5 (cid:2) 1021 cm(cid:3)3, resistivity from 2.1 (cid:2) 10(cid:3)4 to 5.0 (cid:2) 10(cid:3)5 X(cid:4)cm, and Hall mobility from 66 to 97 cm2/V(cid:4)s. Secondary ion mass spectroscopy (SIMS) was used to determine film compositions. Finally, density functional theory (DFT) was used to compute the activation energies for various point defects including nitrogen and scandium vacancies and oxygen and fluorine substituting for nitrogen. For both oxygen and fluorine substitution, the energies were negative, indicating spontaneous formation. Nevertheless, the combined results of the Hall, SIMS, and DFT strongly suggest that oxygen substitution is the primary mechanism behind the high carrier concentration in these samples.
关键词： degenerate n-type semiconductor,Hall-effect measurements,Scandium nitride,density functional theory,electronic transport properties
更新于2025-09-23 15:21:21
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Structure and Electron Mobility of ScN Films Grown on α-Al2O3(1 1 ˉ 02) Substrates
摘要： Scandium nitride (ScN) films were grown on α-Al2O3(1102) substrates using the molecular beam epitaxy method, and the heteroepitaxial growth of ScN on α-Al2O3(1102) and their electric properties were studied. Epitaxial ScN films with an orientation relationship (100)ScN || (1102)α-Al2O3 and [001]ScN || [1120]α-Al2O3 were grown on α-Al2O3(1102) substrates. Their crystalline orientation anisotropy was found to be small. In addition, [100] of the ScN films were tilted along [1101] of α-Al2O3(1102) in the initial stage of growth. The tilt angle between the film growth direction and [100] of ScN was 1.4–2.0? and increased with growth temperature. The crystallinity of the ScN films also improved with the increasing growth temperature. The film with the highest Hall mobility was obtained at the boundary growth conditions determined by the relationship between the crystallinity and the nonstoichiometric composition because the film with the highest crystallinity was obtained under the Sc-rich growth condition. The decreased Hall mobility with a simultaneous improvement in film crystallinity was caused by the increased carrier scattering by the ionized donors originating from the nonstoichiometric composition.
关键词： heterostructure,electric property,scandium nitride,thin film
更新于2025-09-19 17:15:36
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Infrared-laser based characterization of the pyroelectricity in AlScN thin-films
摘要： A measurement system for characterization of the pyroelectricity in thin- and thick-films is introduced. The system is based on a quantum-cascade infrared laser that stimulates the temperature within the sample film with variable modulation frequencies up to 120 kHz. As model material system we choose Scandium-doped Aluminum Nitride (AlScN) due to its promising piezo- and dielectric behavior as well as CMOS compatibility. We measured the pyro-electric response and its temperature characteristics. The transverse effective piezoelectric coefficient e31 is derived from the measurement of the longitudinal effective piezoelectric modulus d33 and we discuss the contribution of piezoelectric clamping to the measured pyroelectric response. Our findings are important for integration of AlScN films on exposed membranes for dense and sensitive infrared detectors.
关键词： Pyroelectric,AlScN,Piezoelectric,Aluminum-scandium-nitride
更新于2025-09-11 14:15:04