Al1−xScxN Thin Films at High Temperatures: Sc-Dependent Instability and Anomalous Thermal Expansion

Ferroelectric thin films of wurtzite-type aluminum scandium nitride (Al1−xScxN) are promising candidates for non-volatile memory applications and high-temperature sensors due to their outstanding functional and thermal stability exceeding most other ferroelectric thin film materials. In this work, the thermal expansion along with the temperature stability and its interrelated effects have been investigated for Al1−xScxN thin films on sapphire Al2O3(0001) with Sc concentrations x (x = 0, 0.09, 0.23, 0.32, 0.40) using in situ X-ray diffraction analyses up to 1100 °C. The selected Al1−xScxN thin films were grown with epitaxial and fiber textured microstructures of high crystal quality, dependent on the choice of growth template, e.g., epitaxial on Al2O3(0001) and fiber texture on Mo(110)/AlN(0001)/Si(100). The presented studies expose an anomalous regime of thermal expansion at high temperatures >~600 °C, which is described as an isotropic expansion of a and c lattice parameters during annealing. The collected high-temperature data suggest differentiation of the observed thermal expansion behavior into defect-coupled intrinsic and oxygen-impurity-coupled extrinsic contributions. In our hypothesis, intrinsic effects are denoted to the thermal activation, migration and curing of defect structures in the material, whereas extrinsic effects describe the interaction of available oxygen species with these activated defect structures. Their interaction is the dominant process at high temperatures >800 °C resulting in the stabilization of larger modifications of the unit cell parameters than under exclusion of oxygen. The described phenomena are relevant for manufacturing and operation of new Al1−xScxN-based devices, e.g., in the fields of high-temperature resistant memory or power electronic applications.

[1]  Md. Redwanul Islam,et al.  From Fully Strained to Relaxed: Epitaxial Ferroelectric Al1‐xScxN for III‐N Technology , 2022, Advanced Functional Materials.

[2]  H. Funakubo,et al.  Demonstration of ferroelectricity in ScGaN thin film using sputtering method , 2021, Applied Physics Letters.

[3]  Z. Mi,et al.  Fully epitaxial ferroelectric ScGaN grown on GaN by molecular beam epitaxy , 2021, Applied Physics Letters.

[4]  Z. Mi,et al.  N-polar ScAlN and HEMTs grown by molecular beam epitaxy , 2021, Applied Physics Letters.

[5]  J. Maria,et al.  Strongly temperature dependent ferroelectric switching in AlN, Al1-xScxN, and Al1-xBxN thin films , 2021, Applied Physics Letters.

[6]  A. Dejneka,et al.  Anisotropic chemical expansion due to oxygen vacancies in perovskite films , 2021, Scientific Reports.

[7]  O. Ambacher,et al.  On the exceptional temperature stability of ferroelectric Al1-xScxN thin films , 2021, Applied Physics Letters.

[8]  J. Maria,et al.  Ferroelectricity in boron-substituted aluminum nitride thin films , 2021, Physical Review Materials.

[9]  M. Caro,et al.  Stability and residual stresses of sputtered wurtzite AlScN thin films , 2021, Physical Review Materials.

[10]  O. Ambacher,et al.  Improved AlScN/GaN heterostructures grown by metal-organic chemical vapor deposition , 2021 .

[11]  S. Nayak,et al.  Clustering of oxygen point defects in transition metal nitrides , 2021 .

[12]  H. Hug,et al.  Mapping the Structure of Oxygen-Doped Wurtzite Aluminum Nitride Coatings from Ab Initio Random Structure Search and Experiments. , 2021, ACS applied materials & interfaces.

[13]  Z. Mi,et al.  Oxygen defect dominated photoluminescence emission of ScxAl1−xN grown by molecular beam epitaxy , 2021 .

[14]  Md. Redwanul Islam,et al.  Atomic scale confirmation of ferroelectric polarization inversion in wurtzite-type AlScN , 2021 .

[15]  R. Olsson,et al.  Post-CMOS Compatible Aluminum Scandium Nitride/2D Channel Ferroelectric Field-Effect-Transistor Memory. , 2020, Nano letters.

[16]  H. Funakubo,et al.  Thickness scaling of (Al0.8Sc0.2)N films with remanent polarization beyond 100 μC cm−2 around 10 nm in thickness , 2021, Applied Physics Express.

[17]  J. Maria,et al.  Ferroelectrics everywhere: Ferroelectricity in magnesium substituted zinc oxide thin films , 2021 .

[18]  O. Ambacher,et al.  First-principles calculation of electroacoustic properties of wurtzite (Al,Sc)N , 2020, Physical Review B.

[19]  D. Jena,et al.  Oxygen Incorporation in the Molecular Beam Epitaxy Growth of ScxGa1−xN and ScxAl1−xN , 2019, physica status solidi (b).

[20]  O. Ambacher,et al.  Experimental determination of the electro-acoustic properties of thin film AlScN using surface acoustic wave resonators , 2019, Journal of Applied Physics.

[21]  O. Ambacher,et al.  Optical constants and band gap of wurtzite Al1−xScxN/Al2O3 prepared by magnetron sputter epitaxy for scandium concentrations up to x = 0.41 , 2019, Journal of Applied Physics.

[22]  B. Wagner,et al.  AlScN: A III-V semiconductor based ferroelectric , 2018, Journal of Applied Physics.

[23]  Paul Muralt,et al.  Abnormal Grain Growth in AlScN Thin Films Induced by Complexion Formation at Crystallite Interfaces , 2018, physica status solidi (a).

[24]  O. Ambacher,et al.  Investigation of Temperature Characteristics and Substrate Influence on AlSeN-Based SAW Resonators , 2018, 2018 IEEE International Ultrasonics Symposium (IUS).

[25]  T. Baumbach,et al.  Real time in situ x-ray diffraction study of the crystalline structure modification of Ba0.5Sr0.5TiO3 during the post-annealing , 2018, Scientific Reports.

[26]  O. Ambacher,et al.  Elastic modulus and coefficient of thermal expansion of piezoelectric Al1−xScxN (up to x = 0.41) thin films , 2018, APL Materials.

[27]  O. Ambacher,et al.  Temperature Dependence of the Pyroelectric Coefficient of AlScN Thin Films , 2018 .

[28]  K. V. Van Vliet,et al.  Atomic Resolution Imaging of Nanoscale Chemical Expansion in PrxCe1-xO2-δ during In Situ Heating. , 2018, ACS nano.

[29]  D. Katzer,et al.  (Invited) ScAlN: A Novel Barrier Material for High Power GaN-Based RF Transistors , 2017 .

[30]  B. Wagner,et al.  Identifying and overcoming the interface originating c-axis instability in highly Sc enhanced AlN for piezoelectric micro-electromechanical systems , 2017 .

[31]  S. Kohara,et al.  Formation of metallic cation-oxygen network for anomalous thermal expansion coefficients in binary phosphate glass , 2017, Nature Communications.

[32]  M. Preuss,et al.  Evolution of dislocation structure in neutron irradiated Zircaloy-2 studied by synchrotron x-ray diffraction peak profile analysis , 2017 .

[33]  P. Frach,et al.  Effect of scandium content on structure and piezoelectric properties of AlScN films deposited by reactive pulse magnetron sputtering , 2017 .

[34]  H. Henein,et al.  Characterization of Precipitates in a Microalloyed Steel Using Quantitative X-ray Diffraction , 2016 .

[35]  B. Wagner,et al.  Stress controlled pulsed direct current co-sputtered Al1−xScxN as piezoelectric phase for micromechanical sensor applications , 2015 .

[36]  S. Bishop,et al.  Strongly coupled thermal and chemical expansion in the perovskite oxide system Sr(Ti,Fe)O3−α , 2015 .

[37]  Kentaro Furusawa,et al.  Impacts of Si-doping and resultant cation vacancy formation on the luminescence dynamics for the near-band-edge emission of Al0.6Ga0.4N films grown on AlN templates by metalorganic vapor phase epitaxy , 2013 .

[38]  Shujun Zhang,et al.  Piezoelectric Materials for High Temperature Sensors , 2011 .

[39]  G. Wingqvist,et al.  Wurtzite-structure Sc1-xAlxN solid solution films grown by reactive magnetron sputter epitaxy structural characterization and first-principles calculations , 2010 .

[40]  G. Wingqvist,et al.  Origin of the anomalous piezoelectric response in wurtzite Sc(x)Al(1-x)N alloys. , 2010, Physical review letters.

[41]  L. Hultman,et al.  Cubic Sc1―xAlxN solid solution thin films deposited by reactive magnetron sputter epitaxy onto ScN(111) , 2009 .

[42]  Nobuaki Kawahara,et al.  Enhancement of Piezoelectric Response in Scandium Aluminum Nitride Alloy Thin Films Prepared by Dual Reactive Cosputtering , 2009, Advanced materials.

[43]  C. Humphreys,et al.  The effect of oxygen incorporation in sputtered scandium nitride films , 2008 .

[44]  P. Koidl,et al.  X-ray determination of the composition of partially strained group-III nitride layers using the Extended Bond Method , 2002 .

[45]  M. Eldrup,et al.  Studies of defects and defect agglomerates by positron annihilation spectroscopy , 1997 .

[46]  Robert A. Youngman,et al.  Luminescence Studies of Oxygen‐Related Defects In Aluminum Nitride , 1990 .

[47]  J. Harris,et al.  On the nature of the oxygen-related defect in aluminum nitride , 1990 .

[48]  R. J. Paff,et al.  Thermal expansion of AlN, sapphire, and silicon , 1974 .