(Color online) Possible gate leakage mechanisms at metal-semiconductor [(a)–(c)] and metal–insulator–semiconductor (d) interfaces.
(a) Unified model for near-surface electronic states of AlGaN, (b) a combined distribution of state density, and (c) the TSB model for current transport at the Schottky interface. Reprinted from Hasegawa et al., J. Vac. Sci. Technol. B 21, 1844 (2003). Copyright 2003, American Vacuum Society.
(Color online) (a) Schematic representation of drain current collapse. Models presented for current collapse (b) under drain stress and (c) under gate stress. Reprinted from Hasegawa et al., J. Vac. Sci. Technol. B 21, 1844 (2003). Copyright 2003, American Vacuum Society.
Model of device showing the location of the virtual gate and schematic representation of the device including the virtual gate. Reprinted from Vetury et al., IEEE Trans. Electron Devices 48, 560 (2001). Copyright 2002, Institute of Electrical and Electronics Engineers.
Crystal structure, spontaneous polarization fields (PSP ), and piezoelectric polarization fields (PPE ) for GaN (top) and AlxGa(a−x)N (bottom). Reprinted from Yu et al., J. Vac. Sci. Technol. B 17, 1742 (1999). Copyright 1999, American Vacuum Society.
(Color online) Band bending schematic for Ga- and N-face GaN. Both surfaces are screened by ∼1013 charges/cm2. (NOTE: the position of the ionized donors and electrons in the material corresponds to their physical position rather than their energy level within the band gap.)
Schematic top view of the vacancy and the vacancy complex. The atomic positions of the first two layers (three layer vacancy complex) are displayed. Open and closed circles represent first- and second-layer atoms. For anion termination, the white and black circles correspond to nitrogen and group-III atoms, respectively. For the case of the cation-terminated surface, the open and closed circles illustrate first-layer group-III atoms and second-layer nitrogen. The p(2×2) unit cell used in all calculations is indicated. Reprinted from Fritsch et al., Phys. Rev. B 57, 15360 (1998). Copyright 1998, American Physical Society.
Schematic of the metal–semiconductor interface models according to (a) Schottky–Mott, (b) Bardeen–Heine, and (c) Tersoff.
Schematic representation of the interface defect densities according to (a) the MIGS model, (b) the unified defect model, and (c) the DIGS model (or the positional surface disorder model).
Schematic of suggested defect mechanism due to deposition of metal atoms on clean III-V surfaces. This process (i.e., a defect must be formed) needs to occur only about once for every hundred metal atoms striking the surface to account for Fermi level pinning. Reprinted from Spicer et al., J. Vac. Sci. Technol. 16, 1422 (1979). Copyright 1980, American Vacuum Society.
Unified DIGS model explaining the correlation between I-S and M-S interfaces. Surface disorder introduces DIGS whose density depends on the degree of disorder (I: good I-S interface, II: poor I-S interface, and III M-S interface). The physical meaning of ECNL can be interpreted as the Fermi energy of the DIGS spectrum where charge neutrality is achieved. ECNL is the branch point between the bonding and antibonding states in the gap. Reprinted from Hasegawa and Ohno, J. Vac. Sci. Technol. B 4, 1130 (1986). Copyright 1986, American Vacuum Society.
CNL is a weighted average of the density of states. It is repelled by a large density of states in the valence or conduction band. Reprinted from Robertson and Falabretti, J. Appl. Phys. 100, 014111 (2006). Copyright 2006, American Institute of Physics.
(Color online) Trend of the CNL/band gap ratio vs. (a) Harrison's bond polarity and (b) ionicity of Garcia and Cohen. As the band gap becomes more direct with higher ionicity, the CNL moves higher in the gap. Reprinted from Robertson and Falabretti, J. Appl. Phys. 100, 014111 (2006). Copyright 2006, American Institute of Physics.
Calculated band offsets of dielectrics on GaN. Reprinted from Robertson and Falabretti, J. Appl. Phys. 100, 014111 (2006). Copyright 2006, American Institute of Physics.
Material properties of Si, GaAs, SiC, and GaN, where μ is the mobility, ε is the relative permittivity, Eg is the band gap energy, the BFOM ratio is the Baliga figure of merit (related to the conduction loss at low frequency), and Tmax is the maximum temperature before degradation of the material. Reprinted from Mishra et al., Proc. IEEE 90, 1022 (2002). Copyright 2002, Institute of Electrical and Electronics Engineers.
Competitive advantages of GaN-based devices. Reprinted from Mishra et al., Proc. IEEE 90, 1022 (2002). Copyright 2002, Institute of Electrical and Electronics Engineers.
Lattice constants [(a) and (c)], piezoelectric constants (e31 and e33), elastic constants (C13 and Ccc), spontaneous polarization (PSP), and polarization bound charge (ρ) of GaN and AlN. The lattice and piezoelectric constants (e31 and e33) as well as the spontaneous polarization are determined by the generalized gradient calculation as described in Ref. 106 . The elastic constants are determined by an average of the values presented in Refs. 96–104 . Values for AlxGa(1−x)N may be determined by linear interpolation.
Summary of band gap, electron affinity, and charge neutrality levels for GaN and AlN, where the CNL is included for several different methods of calculation including the tight binding (ETB) (Ref. 143 ), LDA (Ref. 141 ), and two different first principle (FP) calculations (Refs. 146 and 148 ) as well as the experimental values (Refs. 149–152 ), which are deduced from Schottky barrier measurements.
Valence band and conduction band offsets calculated for dielectrics on GaN as calculated by the local density approximation and charge neutrality level model (Refs. 141 and 189 ). All band offsets are given in eV.
Valence band and conduction band offsets measured for dielectrics on GaN. If one of the offsets is deduced from the measured band offset and the band gap, it is denoted with “a.” The deposition method is noted, where ALD = atomic layer deposition, dry term. ox. = dry thermal oxidation, E-beam = electron beam, ECR = electron cyclotron resonance, MBD = molecular beam deposition, PEALD = plasma-enhanced atomic layer deposition, PECVD = plasma-enhanced chemical vapor deposition, PEMBD = plasma-enhanced molecular beam deposition, and pulsed laser = pulsed laser deposition. In addition, the characterization method is noted, where CV = capacitance-voltage measurements, EELS = electron energy loss spectroscopy, PL = photoluminescence, UPS = ultraviolet photoelectron spectroscopy, UV = UV adsorption, UV-vis = UV-visible adsorption, and XPS = x-ray photoelectron spectroscopy. All offsets are given in eV.
Theoretical and experimental band offsets on AlGaN. The deposition method is noted where ECR-CVD = electron cyclotron resonance chemical vapor deposition, MBD = molecular beam deposition, and vap. cooling cond. = vapor cooling condensation. In addition, the characterization method is noted where EELS = electron energy loss spectroscopy, and XPS = x-ray photoelectron spectroscopy. All offsets are given in eV.
Theoretical and experimental band offsets on AlN. Note the experimental band offsets for InN/AlN are given for the Al-face and the N-face, respectively. The deposition method is noted where MOCVD = metal organic chemical vapor deposition, and PEMBD = plasma-enhanced molecular beam deposition. In addition, the characterization method is noted, where XPS = x-ray photoelectron spectroscopy. All offsets are given in eV.
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