Indium incorporation in homoepitaxial β-Ga2O3 thin films grown by metal organic vapor phase epitaxy

Abstract

Homoepitaxial β-(In,Ga) 2 O 3 thin films were grown on (100) β-Ga 2 O 3 substrates by metal organic vapor phase epitaxy using triethylgallium (TEGa) and triethylindium (TEIn). Deposition temperatures from 650 to 825°C and pressures from 5 to 20 mbar have been explored. The growth rate decreased linearly with increasing deposition temperature and decreased exponentially with increasing pressure. The resulting films were characterized by atomic force microscopy (AFM), high resolution x-ray diffraction (HR-XRD), and transmission electron microscopy (TEM). As the flow rate of TEIn varied from 0 to 0.13 μmol/min during the growth, AFM showed the surface roughness of about 1 nm, while HR-XRD measurements revealed an increase of the vertical lattice spacing. The maximum atomic concentration of indium incorporated in monoclinic β-(In,Ga) 2 O 3 is about 3.5% and shifts the optical absorption edge to lower energy by ∼0.18 eV. Further increase of the indium flow rate leads to an increase of the surface roughness and a decrease in the vertical lattice spacing due to the formation of a separate cubic In 2 O 3 phase that was confirmed by HR-TEM images. X-ray reciprocal space maps showed that the β-(In,Ga) 2 O 3 thin films were grown coherently on β-Ga 2 O 3 .

Investigating the ranges of (meta)stable phase formation in (InxGa1−x)2O3Wouters1, Sutton2, Ghiringhelli3 et al. 2020Phys. Rev. MaterialsSelf Cite18071View full textAdd to dashboardCite

“…For the films grown by PLD and molecular beam epitaxy (MBE), this follows from the fact that during growth, the surface diffusion allows the atoms to locally find their preferred position and preferred coordination environment, so that the low energy but metastable ordered monoclinic and hexagonal phases can be achieved. In β-(In x Ga 1-x ) 2 O 3 grown by metalorganic vapour phase epitaxy (MOVPE) at T = 1100 K [26], which is the growth method closest to thermodynamic equilibrium, the allowed indium incorporation before phase separation takes place does agree well with the predicted thermodynamic limit. For sintered (In x Ga 1-x ) 2 O 3 powders [51] that were heated for several days to reach equilibrium, the measured Ga solubility limit in In 2 O 3 fits well to our calculation of the thermodynamic limit at 1275 K, while the In solubility limit in Ga 2 O 3 falls in the calculated metastable regime.…”

“…7. Additionally, literature data points (triangles) representing indium and gallium solubility limits, respectively, in monoclinic [4,5,26,51] and cubic [51,52] (In x Ga 1-x ) 2 O 3 alloys grown or prepared by different methods have been added.…”

“…7. Additionally, literature data points (triangles) representing indium and gallium solubility limits respectively in monoclinic 4,5,26,48 and cubic 48,49 (InxGa1-x)2O3 alloys grown or prepared by different methods have been added. A first observation is that almost all experimental compositions strongly exceed the narrow calculated thermodynamic stability ranges, and actually fit better to the calculated metastable windows.…”

“…These works are not consistent with experimentally observed indium solubilities. Most experimental work is done on the epitaxial growth of β-(InxGa1-x)2O3 thin films, and different indium solubility limits with different growth methods are found: x<0.4 by solgel 5 , x=0.04 by metalorganic vapor phase epitaxy 26 , x=0.1-0.3 by pulsed laser deposition depending on substrate and growth conditions 27,28 and x=0.35 by molecular beam epitaxy 4 . The work by Holder et al 29 illustrated the possibility for huge metastable composition ranges in heterostructural alloys, which is something that also has to be considered for the (InxGa1-x)2O3 system, since so many polymorphs exist.…”

AlInGaN nanocrystal seeded growth of weak p-type β-(In0.1Ga0.9)2O3 nanowires and nanobelts

“…The epitaxy of (In x Ga 1−x ) 2 O 3 -based materials has been achieved by various methods, e.g. metalorganic chemical vapor deposition, 17,18 and molecular beam epitaxy, 19,20 sputtering, 21,22 solution synthesis, 23 solgel, 24 pulsed-laser deposition, [25][26][27][28] and chemical vapor deposition. [29][30][31][32] (In x Ga 1−x ) 2 O 3 alloys of monoclinic (β), orthorhombic (κ), and bixbyite (bcc) phases have been observed.…”