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α-Ga2O3 has the corundum structure analogous to that of α-Al2O3. The bandgap energy of α-Ga2O3 is 5.3 eV and is greater than that of β-Ga2O3, making the α-phase attractive for devices that benefit from its wider bandgap. The O-H and O-D centers produced by the implantation of H+ and D+ into α-Ga2O3 have been studied by infrared spectroscopy and complementary theory. An O-H line at 3269 cm-1 is assigned to H complexed with a Ga vacancy (VGa), similar to the case of H trapped by an Al vacancy (VAl) in α-Al2O3. The isolated VGa and VAl defects in α-Ga2O3 and α-Al2O3 are found by theory to have a “shifted” vacancy-interstitial-vacancy equlibrium configuration, similar to VGa in β-Ga2O3 which also has shifted structures. However, the addition of H causes the complex with H trapped at an unshifted vacancy to have the lowest energy in both α-Ga2O3 and α-Al2O3. 

There is increasing interest in the alpha polytype of Ga2O3 because of its even larger bandgap than the more studied beta polytype, but in common with the latter, there is no viable p-type doping technology. One option is to use p-type oxides to realize heterojunctions and NiO is one of the candidate oxides. The band alignment of sputtered NiO on α-Ga2O3 remains type II, staggered gap for annealing temperatures up to 600 °C, showing that this is a viable approach for hole injection in power electronic devices based on the alpha polytype of Ga2O3. The magnitude of both the conduction and valence band offsets increases with temperature up to 500 °C, but then is stable to 600 °C. For the as-deposited NiO/α-Ga2O3 heterojunction, ΔEV = −2.8 and ΔEC = 1.6 eV, while after 600 °C annealing the corresponding values are ΔEV = −4.4 and ΔEC = 3.02 eV. These values are 1−2 eV larger than for the NiO/β-Ga2O3 heterojunction.

 

α-Ga₂O₃has the corundum structure analogous to that of α-Al₂O₃. The bandgap energy of α-Ga₂O₃is 5.3 eV and is greater than that of β-Ga₂O₃, making the α-phase attractive for devices that benefit from its wider bandgap. The O–H and O–D centers produced by the implantation of H⁺and D⁺into α-Ga₂O₃have been studied by infrared spectroscopy and complementary theory. An O–H line at 3269 cm⁻¹is assigned to H complexed with a Ga vacancy (V_Ga), similar to the case of H trapped by an Al vacancy (V_Al) in α-Al₂O₃. The isolated V_Gaand V_Aldefects in α-Ga₂O₃and α-Al₂O₃are found by theory to have a “shifted” vacancy-interstitial-vacancy equilibrium configuration, similar to V_Gain β-Ga₂O₃, which also has shifted structures. However, the addition of H causes the complex with H trapped at an unshifted vacancy to have the lowest energy in both α-Ga₂O₃and α-Al₂O₃.