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Journal ArticleDOI

Thermionic trap-assisted tunneling model and its application to leakage current in nitrided oxides and AlGaN∕GaN high electron mobility transistors

11 May 2006-Journal of Applied Physics (American Institute of Physics)-Vol. 99, Iss: 9, pp 093701

Abstract: We propose two models of electron tunneling from metal to a semiconductor via traps. In addition to the electrons below the metal Fermi level, the models also include the thermally activated electrons above the Fermi level. The first model is called generalized thermionic trap-assisted tunneling (GTTT), which considers tunneling through both triangular and trapezoidal barriers present in metal insulator semiconductor (MIS) structures. The second model is called thermionic trap-assisted tunneling (TTT), which considers tunneling through triangular barriers present in modern Schottky junctions. The GTTT model is shown to predict the low field leakage currents in MIS structures with nitrided oxide as insulator, and the TTT model is shown to predict the reverse gate leakage in AlGaN∕GaN high electron mobility transistors.
Topics: Leakage (electronics) (57%), Thermionic emission (54%), Schottky diode (53%), Fermi level (52%), Quantum tunnelling (52%)
Citations
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Journal ArticleDOI
Davide Bisi1, Matteo Meneghini1, Carlo De Santi1, Alessandro Chini2  +5 moreInstitutions (3)
Abstract: This paper critically investigates the advantages and limitations of the current-transient methods used for the study of the deep levels in GaN-based high-electron mobility transistors (HEMTs), by evaluating how the procedures adopted for measurement and data analysis can influence the results of the investigation. The article is divided in two parts within Part I. 1) We analyze how the choice of the measurement and analysis parameters (such as the voltage levels used to induce the trapping phenomena and monitor the current transients, the duration of the filling pulses, and the method used for the extrapolation of the time constants of the capture/emission processes) can influence the results of the drain current transient investigation and can provide information on the location of the trap levels responsible for current collapse. 2) We present a database of defects described in more than 60 papers on GaN technology, which can be used to extract information on the nature and origin of the trap levels responsible for current collapse in AlGaN/GaN HEMTs. Within Part II, we investigate how self-heating can modify the results of drain current transient measurements on the basis of combined experimental activity and device simulation.

248 citations


Additional excerpts

  • ...[26], [55], [67]; or 3) deep-levels charge de-trapping by electron trap-assisted-tunneling mechanisms [14], [15], [54], [60], [70]....

    [...]


Journal ArticleDOI
Lucian Pintilie1, Ionela Vrejoiu1, Dietrich Hesse1, G. LeRhun1  +1 moreInstitutions (1)
Abstract: Leakage current measurements were performed on epitaxial, single-crystal quality $\mathrm{Pb}(\mathrm{Zr},\mathrm{Ti}){\mathrm{O}}_{3}$ films with thicknesses in the $50--300\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$ range. It was found that the voltage behavior of the leakage current has a minor dependence on thickness, which rules out the space-charge limited currents as main leakage source. Temperature-dependent measurements were performed to obtain more information on the transport mechanism through the metal-ferroelectric-metal (MFM) structure. The results are analyzed in the frame of interface-controlled Schottky emission. A surprisingly low value of only $0.12--0.13\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ was obtained for the potential barrier, which is much smaller than the reported value of $0.87\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ [I. Stolichnov et al., Appl. Phys. Lett. 75, 1790 (1999)]. The result is explained by the effect of the ferroelectric polarization on the potential barrier height. The low value of the effective Richardson constant, of the order of ${10}^{\ensuremath{-}7}--{10}^{\ensuremath{-}6}\phantom{\rule{0.3em}{0ex}}\mathrm{A}∕{\mathrm{cm}}^{2}\phantom{\rule{0.2em}{0ex}}{\mathrm{K}}^{2}$, suggests that the pure thermionic emission is not the adequate conduction mechanism for epitaxial MFM structures. The true mechanism might be interface-controlled injection, followed by a low mobility drift through the film volume.

215 citations


Journal ArticleDOI
Abstract: We study electron and hole injection in MoO3 charge generation layers (CGLs) commonly used for establishing balanced injection in multilayer stacked organic light-emitting diodes (SOLEDs). A compound CGL consisting of 100-A-thick MoO3 and Li-doped 4,7-diphenyl-1,10-phenanthroline in a 1:1 molar ratio is demonstrated to have a high electron generation efficiency. Charge injection from the compound CGL is modeled based on a two-step process consisting of tunneling-assisted thermionic emission over an injection barrier of (1.2±0.2) eV and a trap level due to oxygen vacancies at (0.06±0.01) eV above the MoO3 valence band edge. Peak external quantum efficiencies (EQEs) of (10.5±0.2)%, (10.1±0.2)%, (8.6±0.2)%, and (8.9±0.2)% are obtained for tris-(phenylpyridine)iridium-based electrophosphorescent OLEDs with indium tin oxide (ITO) anode/CGL cathode, CGL anode/CGL cathode, CGL anode/Al cathode, and ITO anode/Al cathode contacts, respectively. Based on our analysis, a three-element green emitting electrophosphorescent SOLED is demonstrated with a peak forward-viewing EQE=(24.3±1.0)% and a power efficiency of (19±1) lm/W.

76 citations


Journal ArticleDOI
Xiaofan Jiang1, Zhongyuan Ma1, Jun Xu1, Kunji Chen1  +4 moreInstitutions (1)
TL;DR: The introduction of hydrogen in the a-SiNx:H layer provides a new way to control the Si dangling bond conduction paths, and thus opens up a research field for ultra-low power Si-based RRAM.
Abstract: The realization of ultra-low power Si-based resistive switching memory technology will be a milestone in the development of next generation non-volatile memory. Here we show that a high performance and ultra-low power resistive random access memory (RRAM) based on an Al/a-SiNx:H/p(+)-Si structure can be achieved by tuning the Si dangling bond conduction paths. We reveal the intrinsic relationship between the Si dangling bonds and the N/Si ratio x for the a-SiNx:H films, which ensures that the programming current can be reduced to less than 1 μA by increasing the value of x. Theoretically calculated current-voltage (I-V) curves combined with the temperature dependence of the I-V characteristics confirm that, for the low-resistance state (LRS), the Si dangling bond conduction paths obey the trap-assisted tunneling model. In the high-resistance state (HRS), conduction is dominated by either hopping or Poole-Frenkel (P-F) processes. Our introduction of hydrogen in the a-SiNx:H layer provides a new way to control the Si dangling bond conduction paths, and thus opens up a research field for ultra-low power Si-based RRAM.

57 citations


Journal ArticleDOI
Abstract: This paper reports an investigation of the physical origin of the thermal droop (the drop of the optical power at high temperatures) in InGaN-based light-emitting diodes. We critically investigate the role of various mechanisms including Shockley-Read-Hall recombination, thermionic escape from the quantum well, phonon-assisted tunneling, and thermionic trap-assisted tunneling; in addition, to explain the thermal droop, we propose a closed-form model which is able to accurately fit the experimental data by using values extracted from measurements and simulations and a limited set of fitting parameters. The model is based on a two-step phonon-assisted tunneling over an intermediate defective state, corrected in order to take into account the pure thermionic component at zero bias and the field-assisted term.

53 citations


References
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Journal ArticleDOI
Abstract: In order to clarify the mechanisms of drain current collapse and gate leakage currents in the AlGaN/GaN heterostructure field effect transistor (HFET), detailed electrical properties of the ungated portion and Schottky-gated portion of the device were investigated separately, using a gateless HFET structure and an AlGaN Schottky diode structure. The gateless device was subjected to plasma treatments and surface passivation processes including our novel Al2O3-based surface passivation. dc I–V curves of gateless HFETs were highly nonlinear due to virtual gating by surface states. After drain stress, air-exposed, H2 plasma-treated and SiO2-deposited gateless HFETs showed an initial large-amplitude exponential current transient followed by a subsequent smaller, slow, and highly nonexponential response. The former was explained by emission from deep donors at Ec−0.37 eV, and the latter by emission from surface states. Capture transients with stress-dependent capture barriers were also observed. An x-ray photoe...

197 citations


Journal ArticleDOI
Edward T. Yu1, X. Z. Dang1, L. S. Yu1, D. Qiao1  +5 moreInstitutions (2)
Abstract: A method for enhancing effective Schottky barrier heights in III–V nitride heterostructures based on the piezoelectric effect is proposed, demonstrated, and analyzed. Two-layer GaN/AlxGa1−xN barriers within heterostructure field-effect transistor epitaxial layer structures are shown to possess significantly larger effective barrier heights than those for AlxGa1−xN, and the influence of composition, doping, and layer thicknesses is assessed. A GaN/Al0.25Ga0.75N barrier structure optimized for heterojunction field-effect transistors is shown to yield a barrier height enhancement of 0.37 V over that for Al0.25Ga0.75N. Corresponding reductions in forward-bias current and reverse-bias leakage are observed in current–voltage measurements performed on Schottky diodes.

190 citations


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