Heterogrowth of β-(Al_xGa_1–x)₂O₃ Thin Films on Sapphire Substrates

Abstract

β-(Al x Ga1–x )2O3 films were deposited on c-plane sapphire substrates by metal–organic chemical vapor deposition. Triethylgallium (TEGa), trimethylaluminum (TMAl), and O2 were used as Ga, Al, and O sources, respectively. (−201), (−402), and (−603) diffraction peaks of β-(Al x Ga1–x )2O3 films were observed. The X-ray diffraction peaks shifted to larger diffraction angles and were broadened with the increasing TMAl flow rate or the TMAl/(TMAl + TEGa) flow rate ratio, and the optical band gap was effectively improved. The β-(Al x Ga1–x )2O3 films deposited under different temperatures were further investigated. At 600 °C, Al atoms were more easily incorporated into the crystal lattice, and the optical band gap was improved to 5.73 eV. At 800 and 900 °C, the β-(Al x Ga1–x )2O3 films existed as polycrystalline materials.

The Spatial Correlation and Anisotropy of β-(AlxGa1−x)2O3 Single Crystal

“…The results agreed very well with those reported in the literature [20][21][22]. One must note that the modes belonging to the B 2 g , A 2 g , and A 3 g are associated with the vibration and translation of the [GaO 6 ]-[GaO 4 ] chains; the A 4 g , A 19 g , A 6 g , and A 7 g modes are related to the deformation of the [GaO 6 ] octahedron while A 7 g , A 8 g , and A 10 g phonons are linked to the symmetric stretching and bending vibrational modes of the [GaO 4 ] tetrahedron [17,23]. The perusal of Figure 3a reveals that with an increase in Al composition, the Raman intensity of each band has weakened.…”

“…By carefully increasing Al contents, the band gap of β-(Al x Ga 1−x ) 2 O 3 has the potential to increase from 4.8 eV to 6 eV. This material with higher critical field strength is considered suitable for power electronics devices and shorter cut-off wavelength for optoelectronic devices [5][6][7]. In a recent study [8], the drain current of (Al 0.08 Ga 0.92 ) 2 O 3 /Ga 2 O 3 MODFET (with a gate voltage of +3 V) can be 12 mA mm −1 , and the on/off current ratio is about 10 4 .…”