FIG. 6.2 Calculated formation energy diagrams for shallow donor substitutional Ga-site donor dopants in β-Ga₂O₃ including the group IV elements C, Si, Ge, and Sn. The results are shown for both (a) Ga-rich/O-poor conditions and (b) O-rich/Ga-poor conditions. More about this image found in Calculated formation energy diagrams for shallow donor substitutional Ga-si...

FIG. 6.6 The deep donor level E_d2 at ∼E_C–0.12 eV (a) increases with Si doping in β-Ga₂O₃ ( Ghadi et al., 2020a ) and (b) associated effect of E_d2 level with an estimated increase of on-resistance due to incomplete ionization during forward bias operation of β-Ga₂O₃ Schottky diodes ( Neal et al., 2017 ). More about this image found in The deep donor level E_d2 at ∼

FIG. 6.17 The calculated transition levels of several candidate donor dopants in β-(Al_xGa_1–x)₂O₃ alloys shown as a function of Al content, as adapted with permission from (a) Varley et al., Appl. Phys. Lett. 116 , 172104 (2020). Copyright 2020 AIP Publishing LLC and (b) Mu et al., Phys. Rev. B 105 (2022). Copyright 2020 AIP Publishing LLC. The lines denote the ε(±) transition for C, Si, and Sn, and the ε(±) transition for Ge, Zr, Hf, and Ta dopants on the most favorable cation sites. The CBM energy (shaded green and yellow) is plotted with respect to the VBM energy of Ga₂O₃ for all compositions using the calculated energies from Peelaers et al. (2018) . The Al content at which a given dopant's defect level falls within the bandgap and thus the dopant is no longer expected to efficiently ionize at room temperature is included in parentheses. More about this image found in The calculated transition levels of several candidate donor dopants in β-(A...

FIG. 6.1 Schematic diagram of the behavior of dopants or impurities that act as (a) shallow donors, (b) shallow acceptors, or (c) introduce deep levels that may change occupancy depending on the position of the Fermi level (ε_F). Ga₂O₃ has been shown to exhibit a number of shallow donor candidates as in (a) and deep levels as in (c) that may act as donors and/or acceptors, but no shallow acceptors as in (b) due to fundamental limitations of the electronic structure. More about this image found in Schematic diagram of the behavior of dopants or impurities that act as (a) ...

FIG. 6.5 Silicon dopant energy level detected from (a) temperature-dependent Hall concentration fitted with two-donor model showing a shallow donor level at 40 meV and deep donor level at 150 meV ( Feng et al., 2020 ). (b) The secondary level was also observed from admittance spectroscopy (capacitance–frequency at different temperatures). The arrow indicates the presence of inflection point in the C–f plot associated with the deep trap emission that causes dispersion at higher frequencies ( Neal et al., 2017 ). More about this image found in Silicon dopant energy level detected from (a) temperature-dependent Hall co...

FIG. 1.7 Deep levels in Al_xGa_1-xN as a function of Al composition showing shallow to deep level transition of donor levels as the material transforms from WBG GaN to UWBG Al_xGa_1-xN ( Kamyczek et al., 2012 ). More about this image found in Deep levels in Al_xGa_1-xN as a function of Al composit...

FIG. 6.12 Formation energy diagram for Mg dopants in β-Ga₂O₃ shown for (a) Ga-rich (O-poor) and (b) O-rich (Ga-poor) conditions as adapted from Ritter et al., Appl. Phys. Lett. 113 (5), 052101 (2018). Copyright 2018 AIP Publishing LLC and Peelaers et al., APL Mater. 7 (2), 022519 (2019). Copyright 2019 AIP Publishing LLC. The figures also illustrate that moving the Fermi level away from the CBM with acceptor doping can also enhance the incorporation of donors such as deep donor Ir_Ga impurities which were shown to be present in higher concentrations in Mg-doped single crystals ( Ritter et al., 2018 ). More about this image found in Formation energy diagram for Mg dopants in β-Ga₂O₃ sh...

FIG. 6.3 Calculated formation energy diagrams for several transition-metal substitutional Ga-site donor dopants in β-Ga₂O₃ shown for both Ga-rich/O-poor conditions (a) and O-rich/Ga-poor conditions (b). Reproduced with permission from Saleh et al., Semicond. Sci. Technol. 35 , 04LT01 (2020). Copyright 2020 AIP Publishing LLC. More about this image found in Calculated formation energy diagrams for several transition-metal substitut...

FIG. 6.8 Sn dopant level (a) detection from temperature-dependent Hall measurements showing the donor energy level at 77 meV ( Mauze et al., 2020 ) and (b) comparison of Sn and Si in terms of available free carrier from Hall measurements vs SIMS concentration showing a drop of carrier concentration from Sn at high doping levels ( Baldini et al., 2016 ). More about this image found in Sn dopant level (a) detection from temperature-dependent Hall measurements ...