FIG. 2.10 Relationship between dopant content in source material and N_d–N_a for EFG grown crystals ( Kuramata et al., 2016 ). More about this image found in Relationship between dopant content in source material and N_d...

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. 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 ...

FIG. 6.10 Fe dopant level detection (a) DLTS studies revealing a defect state at E2 = E_C–0.8 eV that was quite insensitive to radiation indicating an extrinsic source and (b) the E2 level tracks well to increase in Fe concentration from SIMS. Reproduced with permission from Ingebrigtsen et al., Appl. Phys. Lett. 112 , 042104 (2018). Copyright 2018 AIP Publishing LLC. More about this image found in Fe dopant level detection (a) DLTS studies revealing a defect state at

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. 6.12 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. 6.13 (a) Formation energy diagram for N_O dopants in β-Ga₂O₃ shown for Ga-rich conditions. (b) Corresponding atomic structures. (c) Calculated luminescence lines for optical transitions involving electrons in the conduction band recombining with holes at N_O defects. Adapted from Lyons, Semicond. Sci. Technol. 33 (5), 05LT02 (2018). Copyright 2018 AIP Publishing LLC and Frodason et al., J. Appl. Phys. 127 (7), 075701 (2020). Copyright 2020 AIP Publishing LLC. More about this image found in (a) Formation energy diagram for N_O dopants in β-Ga₂O...

FIG. 6.14 Formation energy diagrams for N dopants and related complexes in β-Ga₂O₃ shown for (a) Ga-rich (O-poor) and (b) O-rich (Ga-poor) conditions. Adapted with permission from Peelaers et al., APL Mater. 7 (2), 022519 (2019). Copyright 2019 AIP Publishing LLC. More about this image found in Formation energy diagrams for N dopants and related complexes in β-Ga₂...

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. 1.4 (a) Relationship of bandgap and critical breakdown electric field for direct and indirect semiconductors ( Kaplar et al., 2016 ). (b) Theoretical limits of on-resistance and breakdown field of the semiconductors showing their predicted contours of BFOM ( Tsao et al., 2017 ). Note that the theoretical BFOM contours assume that the dopant is completely ionized, which is often not the case in real WBG and UWBG semiconductors. Hence, a modified BFOM is used to evaluate the true material case accounting incomplete dopant ionization and background compensation effects that is shown later in Fig. 1.6 . More about this image found in (a) Relationship of bandgap and critical breakdown electric field for direc...

FIG. 1.6 (a) Ionized doping concentration in different semiconductors with respect to the background doping considering compensation effect of acceptor-like impurities ( Zhang and Speck, 2020 ). (b) Modified BFOM contour plot estimated from the on-resistance and breakdown field accounting ionized dopants. β-Ga₂O₃ shows the highest BFOM when material purity and dopant ionization efficiency are considered to estimate BFOM. Reproduced with permission from Zhang et al., Semicond. Sci. Technol. 35 (12), 125018. (2020). Copyright 2020 AIP Publishing LLC. More about this image found in (a) Ionized doping concentration in different semiconductors with respect t...

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. 6.7 Effect of (a) growth temperature and (b) Ga flux on Sn and Ge doping in PAMBE growth. The Ge dopants show a drop in concentration likely related to site competition between Ga and Ge. Reproduced with permission from Mauze et al., Appl. Phys. Lett. 117 (22), 222102 (2020). Copyright 2020 AIP Publishing LLC. More about this image found in Effect of (a) growth temperature and (b) Ga flux on Sn and Ge doping in PAM...

FIG. 11.1 (a) Shutter pulsing scheme used to avoid Si source oxidation during growth. (b) SIMS profile of Si dopants showing nearly flat profile while using the delta doping approach. Reproduced with permission from Krishnamoorthy et al., Appl. Phys. Express 10 (5), 051102 ( 2017a ). Copyright 2017 The Japan Society of Applied Physics. More about this image found in (a) Shutter pulsing scheme used to avoid Si source oxidation during growth....

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...