Thermionic trap-assisted tunneling model and its application to leakage current in nitrided oxides and AlGaN∕GaN high electron mobility transistors
TL;DR: In this paper, two models of electron tunneling from metal to a semiconductor via traps are proposed, one called generalized thermionic trap-assisted tunneling (GTTT) and the other one called thermionic trapped-assisted tunnelling (TTT).
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.
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TL;DR: In this paper, a complete model for the metal-oxide-semiconductor capacitors, leakage current mechanisms through the oxide into the semiconductor and small a.c. signal equivalent circuit of the device is proposed and discussed.
Abstract: Metal oxide semiconductor capacitors were fabricated using p-type oxygen-terminated (001) diamond and Al2O3 deposited by atomic layer deposition at two different temperatures 250 °C and 380 °C. Current voltage I(V), capacitance voltage C(V), and capacitance frequency C(f) measurements were performed and analyzed for frequencies ranging from 1 Hz to 1 MHz and temperatures from 160 K to 360 K. A complete model for the Metal-Oxide-Semiconductor Capacitors electrostatics, leakage current mechanisms through the oxide into the semiconductor and small a.c. signal equivalent circuit of the device is proposed and discussed. Interface states densities are then evaluated in the range of 1012eV−1cm−2. The strong Fermi level pinning is demonstrated to be induced by the combined effects of the leakage current through the oxide and the presence of diamond/oxide interface states.
33 citations
TL;DR: In this article, the authors proposed a model for leakage currents in Schottky contacts on InAlN/GaN heterostructures based on two distinct tunneling mechanisms, which are experimentally determined in the first part of this work.
Abstract: We propose a model for leakage currents in Schottky contacts on InAlN/GaN heterostructures based on two distinct tunneling mechanisms. Our modeling relies on structural parameters, in particular, InAlN dielectric constant, interface polarization charges and Schottky barrier height, which are experimentally determined in the first part of our work. The first leakage mechanism is dominant in heterostructures with very thin (≤7 nm) InAlN barriers and consists in tunneling assisted by a deep level located 1.7 eV below the InAlN conduction band edge. We provide experimental evidence for this level through photocapacitance measurements. The second mechanism is on the other hand dominant in thicker InAlN layers and is linked to the appearance of highly doped regions where direct tunneling through the whole InAlN barrier is significantly enhanced. We also show that the two mechanisms may coexist for InAlN layers of intermediate thickness. Our findings confirm a progressive degradation of the InAlN material qualit...
29 citations
TL;DR: In this article, the authors utilize electrically detected magnetic resonance (EDMR), a derivative of electron paramagnetic resonance, to provide physical insight into electronic transport, as well as the nature and origin of defects in dense and porous aSiOC:H and dense a-SiCN:H films.
Abstract: Defect mediated electronic transport phenomena in low-κ dielectric films are of great technological interest for state-of-the-art and next generation microprocessors. At the present time, the leading low-κ interlayer dielectrics and etch-stop layers are based upon a-SiOC:H and a-SiCN:H, respectively. In this study, we utilize electrically detected magnetic resonance (EDMR), a derivative of electron paramagnetic resonance, to provide physical insight into electronic transport, as well as the nature and origin of defects in dense and porous a-SiOC:H and dense a-SiCN:H films. Resonance measurements are performed before and after the removal of sacrificial porogens via UV treatments to understand the role of specific defect centers in electronic transport in a-SiOC:H systems, and the nature of defects created by UV treatments. Unfortunately, a-SiOC:H and a-SiCN:H EDMR spectra are relatively broad and featureless. These featureless spectra are consistent with fairly complex a-SiOC:H and a-SiCN:H systems. We argue that physical insight may be gleaned from featureless spectra via multiple frequency EDMR. Baseline multiple frequency EDMR measurements are performed in a-Si:H and a-C:H to illustrate the nature of line broadening mechanisms of silicon and carbon related defects.
23 citations
TL;DR: In this article, a 4-parameter thermionic trap assisted tunneling model was used to estimate the gate leakage current in AlGaN/GaN HFETs after neutron irradiation.
Abstract: AlGaN/GaN HFET's were cooled to ~85 K and irradiated to a fluence of 1012 n/cm2 (1 MeV equivalent) and gate currents measured. The observed increased gate leakage current was studied by curve-fitting a 4-parameter thermionic trap assisted tunneling model to the experimental measurements. The model parameters were constrained and a least-squares fitting routine was applied to best fit the gate current's voltage and temperature dependence. The results were used to provide an interpretation of the physical changes to the HFET gate following neutron irradiation. The fitting showed that Schottky barrier lowering plays a minor role in post irradiation gate leakage, and trap density and mean trap energy were the dominant post irradiation gate leakage parameters. The ~25% increase in trap density and ~7 mV increase in mean trap energy indicated that neutron elastic collisions produce additional non-native defects within the AlGaN gate region.
23 citations
Cites methods from "Thermionic trap-assisted tunneling ..."
...Thus, a published model by Sathaiya [11], [12] was employed....
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...In order to determine which parameter change dominated the post irradiation current response, the model was fit to the data with all fitting parameters allowed to vary but constrained to valid physical values [11]–[13], using a relative root-mean-square-error minimum (R-RMSE) fit....
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TL;DR: In this paper, the authors investigated the forward gate leakage current in an AlGaN/GaN metal-oxide-semiconductor high-electron-mobility transistor and developed a physics-based analytical model for the trap-assisted tunneling (TAT) mechanism.
Abstract: Investigation of various forward gate leakage current mechanisms in an AlGaN/GaN metal–oxide–semiconductor high-electron-mobility transistor is done in this paper. During high temperature ( $T>388$ K), the trap-assisted tunneling (TAT) mechanism dominates the gate leakage current at low electric field for a range of gate biases from 0 to 0.2 V, whereas the Poole–Frenkel emission is the major component during medium and high electric field. During low temperature ( $T K), TAT alone is dominant and consistent throughout the whole range of electric field. A formulation of vertical electric field, across the oxide and barrier, is framed by incorporating oxide/barrier interface density of states. Then a physics-based compact analytical model for the TAT mechanism is developed and along with the existing PFE model, the forward gate leakage current is calculated. The results of the developed model in different regions of forward gate characteristics are in good agreement with the experimental results available in the literature.
22 citations
Cites background or methods from "Thermionic trap-assisted tunneling ..."
...Sathaiya and Karmalkar [21] have not evaluated the integration in (4) due to complexity and rather opted for numerical solution....
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...P1, P2_tri, and P2_trap are the tunneling probabilities based on WKB approximations for the two step process and expressed as [21]...
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...TAT occurs through both triangular and trapezoidal barriers in a metal–insulator– semiconductor structure, whereas only triangular barrier in a metal–semiconductor structure [21]....
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...Karmalkar et al. [19], [20] demonstrated TAT at temperatures T < 500 K and direct tunneling by thermionic field emission at higher temperatures, which are responsible for reverse leakage current....
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...3(a), where ( EC)oxide/AlGaN is the conduction band offset at the oxide/AlGaN interface and Vb = (q Nbt(2) b )/2εb, Nb is the unintentional doping concentration in barrier, tb is the thickness of barrier, and εb is the permittivity of barrier [21]....
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References
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Book•
01 Jan 1978TL;DR: In this article, a review of the present knowledge of metal-semiconductor contacts is given, including the factors that determine the height of the Schottky barrier, its current/voltage characteristics, and its capacitance.
Abstract: A review is given of our present knowledge of metal-semiconductor contacts. Topics covered include the factors that determine the height of the Schottky barrier, its current/voltage characteristics, and its capacitance. A short discussion is also given of practical contacts and their application in semiconductor technology, and a comparison is made with p-n junctions.
4,279 citations
Book•
01 Jan 2001
TL;DR: The Brillouin Zone for Wurtzite Crystal is defined in this paper, as the first zone for Zinc Blende Crystal, which is a type of hexagonal crystal.
Abstract: Contributors. Preface. Gallium Nitride (GaN) (V. Bougrov, et al.). Aluminum Nitride (AIN) (Y. Goldberg). Indium Nitride (InN) (A. Zubrilov). Boron Nitride (BN) (S. Rumyantsev, et al.). Silicon Carbide (SiC) (Y. Goldberg, et al.). Silicon-Germanium (Si-1-xGe-x) (F. Schaffler). Appendix 1: Basic Physical Constants. Appendix 2: Periodic Table of the Elements. Appendix 3: Rectangular Coordinates for Hexagonal Crystal. Appendix 4: The First Brillouin Zone for Wurtzite Crystal. Appendix 5: Zinc Blende Structure. Appendix 6: The First Brillouin Zone for Zinc Blende Crystal. Additional References.
1,556 citations
TL;DR: In this paper, the authors investigated the mechanisms of drain current collapse and gate leakage currents in the AlGaN/GaN heterostructure field effect transistor (HFET), and detailed electrical properties of the ungated and Schottky-gated portion of the device were investigated separately.
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...
209 citations
TL;DR: In this paper, the gate leakage currents in AlGaN/GaN heterostructure field effect transistor (HFET) structures with conventional and polarization-enhanced barriers have been studied.
Abstract: Gate leakage currents in AlGaN/GaN heterostructure field-effect transistor (HFET) structures with conventional and polarization-enhanced barriers have been studied Comparisons of extensive gate leakage current measurements with two-dimensional simulations show that vertical tunneling is the dominant mechanism for gate leakage current in the standard-barrier HFET and that the enhanced-barrier structure suppresses this mechanism in order to achieve a reduced leakage current An analytical model of vertical tunneling in a reverse-biased HFET gate-drain diode is developed to evaluate the plausibility of this conclusion The model can be fit to the measured data, but suggests that additional leakage mechanisms such as lateral tunneling from the edge of the gate to the drain or defect-assisted tunneling also contribute to the total leakage current The vertical tunneling current mechanism is shown to be more significant to the gate leakage current in III–V nitride HFETs than in HFETs fabricated in other III–V
194 citations