Plan-view TEM observation of a single-domain κ-Ga₂O₃ thin film grown on ε-GaFeO₃ substrate using GaCl₃ precursor by mist chemical vapor deposition

Abstract

We demonstrated the growth of a single-domain κ-Ga2O3 thin film on ε-GaFeO3 by using an organic-free compound as a precursor for mist chemical vapor deposition. X-ray diffraction analysis revealed that an 87-nm-thick κ-Ga2O3 thin film was grown almost coherently with slight lattice relaxation. The surface morphology of the κ-Ga2O3 thin film exhibited a step-terrace structure without island growth. Furthermore, plan-view TEM observations revealed that the κ-Ga2O3 thin film grown on ε-GaFeO3 had a single domain, whereas the previously reported κ-Ga2O3 thin film grown on AlN template had a domain structure.

Electrical and Recombination Properties of Polar Orthorhombic κ-Ga2O3 Films Prepared by Halide Vapor Phase Epitaxy

“…The presence of these rotational domains initially leads to them being incorrectly assigned to the hexagonal symmetry and group symmetry of P63mc, and regarding the material as ε-Ga 2 O 3 [ 25 ] instead of orthorhombic Pna21 κ-Ga 2 O 3 , which is correct. Thus, although a growth of single-domain films has been reported [ 34 ], in most cases, κ-Ga 2 O 3 can be considered to be a nanocrystalline material. The boundaries between these rotational domains present an obstacle to the current flow in the growth plane and, for a long time, have prevented the research of the electrical properties of κ-Ga 2 O 3 films; however, more recently, heterostructures and quantum wells of κ-(Al x Ga 1−x ) 2 O 3 /κ-Ga 2 O 3 with different Al mole fractions and hence different band structures have been demonstrated, and vertical NiO/κ-Ga 2 O 3 structures have been successfully fabricated by pulsed laser deposition [ 35 , 36 ].…”

“…This major disadvantage impairing the practical use of κ-Ga 2 O 3 -based structures and devices was partly overcome in [ 19 ] by employing ELOG growth on sapphire substrates masked with thin TiO 2 and patterned with either stripes or dots of SiO 2 ; this facilitated the formation of single-domain κ-Ga 2 O 3 films with good crystalline quality using HVPE. In addition, the authors of [ 32 , 34 ] were able to prepare single-domain κ-Ga 2 O 3 films using mist CVD growth on the ε-GaFeO 3 substrate. However, neither work detailed the electrical characterization of the κ-Ga 2 O 3 films grown.…”

Observing the microstructure of a (001) κ-Ga2O3 thin film grown on a (−201) β-Ga2O3 substrate using automated crystal orientation mapping transmission electron microscopy

“…Therefore, there is nothing special about the occurrence of rotational domains using a (−201) β-Ga 2 O 3 substrate. Recently, it has been demonstrated that almost lattice-matched ε-GaFeO 3 (001) substrates with κ-Ga 2 O 3 36,37 and the lateral overgrowth on c -plane sapphire substrates 38 prevent the occurrence of this rotational domain. However, the origins of the peaks at around −114°, −72°, 68°, and 108° indicated by blue triangles in Fig.…”

Stress Relaxation Due to Dislocation Formation in Orthorhombic Ga2O3 Films Grown on Al2O3 Substrates

“…However, until now, some works indicate the possibility of the existence of pure ε-phase [12]. Despite the ongoing debate about the real structure of the considered phase, most scientific groups tend to consider the phase as composed of 3-fold rotational orthorhombic domains with disordered domain boundaries [10,11,13,14]; the single-domain orthorhombic structure of this phase has been recently demonstrated [3,15]. Therefore, in this work, we will consider this phase as κ-Ga2O3 with the orthorhombic crystal structure Pna21.…”