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 article, the gate leakage and transistor current were measured and compared to theoretical tunneling models and it was shown that point defects in the AlGaN that are positively charged at low temperature.
Abstract: Al0.27Ga0.73N/GaN HFETs were electron irradiated at ~ 80 K. The gate leakage and transistor current were measured and compared to theoretical tunneling models. The results are consistent with previous work but explicitly show that radiation produces point defects in the AlGaN that are positively charged at low temperature.
19 citations
Cites background or methods from "Thermionic trap-assisted tunneling ..."
...The gate leakage current as a function of temperature was modeled using a four-parameter trap-assisted-tunneling model [15]....
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...The results were fit to a Trap-Assisted Tunneling (TAT) model [15]....
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...TAT model [15] fitting to unpassivated HFET data indicates that is the dominant parameter affecting ....
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...Table III presents pre- to post-irradiation changes of the four TAT model parameters [15] in some of the unpassivated HFETs...
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...sisted Tunneling theory set forth in [15]....
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TL;DR: A comparison of the effect of rapid thermal nitridation (RTN) of the Si surface in N2O and NH3 ambient at different temperatures (700?850??C) on the dielectric and electrical characteristics of thin (~20?nm) Ta2O5 stacks has been made.
Abstract: A comparison of the effect of rapid thermal nitridation (RTN) of the Si surface in N2O and NH3 ambient at different temperatures (700?850??C) on the dielectric and electrical characteristics of thin (~20?nm) Ta2O5 stacks has been made. The electrical parameters of capacitors (film permittivity, oxide charge, densities of bulk traps, interface and slow states, leakage current) are discussed in terms of the impact of N incorporation in the interface region. The films on both types of RTN-treated Si exhibit ~100 times lower leakage current than Ta2O5 on bare Si, but among the two RTN processes NH3 nitridation is more beneficial since only it simultaneously increases also the stack permittivity. This improvement in parameters is suggested to be due to a real nitridation of Si surface which occurs under the NH3 rapid thermal process. RTN in N2O does not produce resistance to the oxidation substrate and it could explain the observed lack of stack dielectric constant improvement. The composition of the interfacial layer under NH3 RTN appears to be TaSi-oxinitride-like, while the interface region at N2O-nitrided Si seems to be SiO2-like. Each RTN process, however, modifies the Si surface and constitutes a specific interface layer different from that at the bare Si substrate. The composition of this layer defines parameters of the traps close to the substrate, the barrier height at the Ta2O5/interface layer and influences the conduction mechanisms in the stacks.
19 citations
19 citations
TL;DR: In this paper, the effects of low energy (0.45 MeV) electron radiation on the gate and drain currents of Al0.27Ga0.73N/GaN HFETs were investigated using IV and CV measurements.
Abstract: The effects of low energy (0.45 MeV) electron radiation on the gate and drain currents of Al0.27Ga0.73N/GaN HFETs are investigated using IV and CV measurements. Following irradiation, the gate and drain currents increase at low temperatures and reach a saturation level. The gate leakage currents do not fully account for the drain current increase. Following a room temperature anneal, the gate and drain currents return to pre-irradiation levels. These results are explained by the buildup of positive charge in the AlGaN layer at low temperature and traps formed via a complexing precursor in the AlGaN layer near the interface. The positive charge increases the carrier concentration in the 2DEG and hence the drain current. The traps act as trap-assisted-tunneling centers that increase the gate leakage current.
19 citations
Cites background or methods or result from "Thermionic trap-assisted tunneling ..."
...Sathaiya and Kalmalkar [22] recently published a physics based model that includes the effects of temperature and the...
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...45 MeV electrons in AlGaN, and fitting of the gate leakage to a thermionic trap-assisted-tunneling (TAT) model [22] confirms that displacement damage is the source of the increased ....
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...26 V for these devices based on simulation with the Thermionic TAT model) [22]....
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...The results of the fitting agree well with the parameters found in the work of [22]....
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...Sathaiya and Kalmalkar [22] recently published a physics based model that includes the effects of temperature and the local electric field on the leakage current in AlGaN/GaN high electron mobility transistors (HEMTs) for unirradiated devices....
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TL;DR: In this article, a closed-form version of the trap-assisted tunneling model is proposed to reveal the peak, energy location and spread of emitted electron distribution, and the model also yields characteristic field parameters to identify the thermally activated regime of current versus field behavior.
Abstract: Recently, we proposed a trap-assisted tunneling model (2006) that includes tunneling of thermally activated electrons above the metal Fermi level for explaining the temperature-dependent leakage current in some semiconductor devices. In the present paper, we develop a closed-form version of this model, which provides physical insight by revealing the peak, energy location and spread of emitted electron distribution. The model also yields characteristic field parameters to identify the thermally activated regime of current versus field behavior and the location of peak emission. The closed-form solution of a complicated equation has been achieved using a geometrical interpretation of the integration operation, and by bisecting the range of trap energies, adopting separate approximations for the bisected segments, and then mathematically combining the two segments into a single continuous function valid for the entire range of trap energies. The closed-form model calculations match well with numerical integration results.
19 citations
Cites background or methods from "Thermionic trap-assisted tunneling ..."
...The device number and model parameters used here are the same as in [1]....
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...These calculations Z(φ) = 1( {1 + exp [(φB − φ)/Vt ]} exp { (α/E)[φ3/2 − φ3/2t ] }) + exp { (α/E)φ3/2t } , for φ ≥ φt (9) have been performed for material parameters corresponding to the Schottky gate junction of an AlGaN/GaN HEMT....
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...This model could explain the measured anomalous large leakage current flowing through the Schottky type gate junction of AlGaN/GaN HEMTs [1], [6]....
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...Recently we, [1] proposed a model called thermionic trap-assisted tunneling (TTT), which includes tunneling of thermally activated electrons above the metal Fermi level (see Fig....
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...TRAP-ASSISTED tunneling (TT) is widely regarded to be the mechanism of the leakage current through nitrided tunnel oxides [1]–[5]....
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References
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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.
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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