Growth and Band Gap Control of Corundum-Structured α-(AlGa)₂O₃ Thin Films on Sapphire by Spray-Assisted Mist Chemical Vapor Deposition

Abstract

Following the previous achievement of highly crystalline α-Ga2O3 thin films on c-plane sapphire, the growth of corundum-structured α-(Al x Ga1-x )2O3 was examined aiming at the future application of α-(Al x Ga1-x )2O3/Ga2O3 heterostructures to power devices and other functional devices. The results show the control of x and band gap up to 0.81 and 7.8 eV, respectively, maintaining the dominant corundum structure. The transmission electron microscope observation suggested the formation of the crystallographically good interface of α-(Al x Ga1-x )2O3/Ga2O3 without the severe generation of threading dislocation lines from the interface.

Identification and modulation of electronic band structures of single-phase β-(AlxGa1−x)2O3 alloys grown by laser molecular beam epitaxy

“…Similar phenomena have also been observed in the hetero-epitaxial growth of (Al x Ga 1Àx ) 2 O 3 on sapphire by various means of MBE, pulsed laser deposition (PLD), and, MIST-CVD techniques. 10,18,19 The reported phase transition from a stable pseudomorphic a-(Al x Ga 1Àx ) 2 O 3 ultra-thin interfacial layer into a plastically relaxed and textured monoclinic b-(Al x Ga 1Àx ) 2 O 3 in the form of rotational domains is also observed, as shown in supplementary material, Fig. S2.…”

“…20 The crystalline degradation is attributable to the relatively low growth temperature for crystallization of b-(Al x Ga 1Àx ) 2 O 3 as it is optimized for pure b-Ga 2 O 3 . 10,18,19 Nevertheless, the dominant (À6 0 3) diffraction peaks indicate the grown films are of the single phase with a preferred (À2 0 1) orientation. Figure 1(b) exhibits that the position of the (À6 0 3) peaks shows a monotonic shift to the higher angle side, which suggests a shrinking in the lattice constant of (À2 0 1) due to the smaller ionic radius of the Al 3þ ions substituting Ga 3þ ions.…”

Temperature dependence of Raman scattering in β-(AlGa)2O3 thin films

“…For Al 2 O 3 film, almost no peak can be observed except the Raman peak of sapphire substrates. Figure 3 shows the dependence of the spectral positions of A g (3) , A g (9) /B g (5) , and A g (10) phonon modes on the Al content. As shown in figure 3, the Al content range of 0-0.72 the A g (3) phonon mode exhibits a shift of ∼41 cm −1 , the A g (9) /B g (5) phonon mode has a shift of ∼65 cm −1 , and the shift is A g (10) phonon modes is ∼46 cm −1 .…”

“…[1][2][3][4] As a wide variable bandgap semiconductor, ternary (AlGa) 2 O 3 is a promising candidate for deep ultraviolet optoelectronic device applications because (AlGa) 2 O 3 has an advantage of large tunable bandgaps from 4.8 eV (Ga 2 O 3 ) to 8.6 eV (Al 2 O 3 ) at room temperature. 5,6 In order to realize (AlGa) 2 O 3 application in deep ultraviolet optoelectronic devices, great efforts have made remarkable progress for growing this alloy. 7 In our previous experiment, (AlGa) 2 O 3 thin films were successfully deposited by pulsed laser deposition (PLD), and β-(AlGa) 2 O 3 thin film could be obtained in the Al content range of 0-0.72.…”

Ordinary dielectric function of corundumlike α−Ga2O3 from 40 meV to 20 eV

“…The possibility to create alloys [23] with α-In 2 O 3 [24][25][26][27][28] or α-Al 2 O 3 is a further invaluable advantage. Consequently, the growth of phase pure alloys [29] and advanced functional heterostructures is possible [30].…”