Stress–strain state and piezoelectric polarization in orthorhombic Ga2O3 thin films depending on growth orientation

• Published in: Materials & design 2023-02, Vol.226, p.111616, Article 111616
• Main Authors: Smirnov, A.M., Kremleva, A.V., Ivanov, A.Yu, Myasoedov, A.V., Sokura, L.A., Kirilenko, D.A., Sharofidinov, Sh.Sh, Romanov, A.E.
• Format: Article
• Language: English
• Subjects: Orientation relationships; Orthorhombic Ga2O3; Piezoelectric polarization; Stress–strain state; Thin films
• ISSN: 0264-1275; 1873-4197
• DOI: 10.1016/j.matdes.2023.111616

[Display omitted] •k-Ga2O3 is grown epitaxially on α-Al2O3 with 100 || 1¯21¯0, 010 || 1¯010 and [001] || [0001] orientation relationships.•Analytical expressions for describing the stress-strain state and piezoelectric polarizations in films of κ-Ga2O3/α-Al2O3 and κ-(AlxGa1–x)2O3/κ-Al2O3 heterostructures taking into account materials anisotropy and various growth orientations are presented.•Heterostructure growth orientations can be used to design mechanical and electrical properties of κ-Ga2O3 film, for example, κ-Ga2O3/α-Al2O3 heterostructures with exotic(101¯8), (101¯3), and (21¯1¯5) growth planes, and κ-(AlxGa1–x)2O3/κ-Al2O3 heterostructures with ordinary (010) and (100) growth planes can be characterized by a low level of internal stresses and low or zero values of strain-induced piezoelectric polarization in the film. The experimental data on orientation relationships for halide vapor phase epitaxy (HVPE) κ-Ga2O3 film grown on (0001) α-Al2O3 substrate and the theoretical model that describes growth orientation dependences of stress–strain state and piezoelectric polarization in κ-(AlxGa1-x)2O3 films with orthorhombic crystal structure grown on α-Al2O3 and κ-Al2O3 substrates are presented. Two possibilities for variation in films growth orientation for κ-Ga2O3/α-Al2O3 and κ-(AlxGa1–x)2O3/κ-Al2O3 heterostructures with inclination axes about either [100] or [010] crystallographic directions are considered. The changes in elastic strain field and piezoelectric polarization in the film caused by the differences in values of lattice parameters, elastic, and piezoelectric constants are demonstrated. The growth planes for κ-Ga2O3/α-Al2O3 and κ-(AlxGa1–x)2O3/κ-Al2O3 heterostructures that are characterized by low internal stresses and low or zero values of piezoelectric polarization are found.