A model for the high field leakage current in nitrided oxides
TL;DR: In this paper, a generalized thermionic trap-assisted tunneling model was proposed to predict both high and low field leakage currents if a fraction (∼35%) of the insulator thickness located next to the metal-insulator junction is devoid of traps.
Abstract: The enhanced conduction at low fields (<4MV∕cm) in metal-insulator semiconductor structures having nitrided oxides was recently explained using a generalized thermionic trap-assisted tunneling model. In the present work, we show that the same model can predict both high and low field leakage currents if we assume that a fraction (∼35%) of the insulator thickness located next to the metal-insulator junction is devoid of traps.
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TL;DR: In this article, the trapping phenomena in GaN metal-oxide-semiconductor high-electron mobility transistor structures with 10 and 20-nm thick Al2O3 gate dielectric grown by metal-organic chemical vapor deposition were deeply investigated using comprehensive capacitance-voltage measurements.
Abstract: The trapping phenomena in GaN metal-oxide-semiconductor high-electron mobility transistor structures with 10 and 20-nm thick Al2O3 gate dielectric grown by metal-organic chemical vapor deposition were deeply investigated using comprehensive capacitance-voltage measurements. By controlling the interface traps population, substantial electron trapping in the dielectric bulk was identified. Separation between the trapping process and the interface traps emission allowed us to determine distribution of interface trap density in a wide energy range. Temperature dependence of the trapping process indicates thermionic field emission of electrons from the gate into traps with a sheet density of ∼1013 cm−2, located a few nm below the gate.
57 citations
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26 Oct 2012
TL;DR: In this article, the gate leakage currents increased after low temperature irradiation and the increase was persistent after room temperature annealing, which was attributed to trap-assisted tunneling after application of the trap assisted tunneling model.
Abstract: : AlGaN/GaN Heterojunction Field Effect Transistors (HFETs) were irradiated at low temperature and the temperature dependent changes to drain current, gate current, capacitance, and transconductance were measured. The results were compared to the charge control model of the drain current and trap-assisted tunneling model of the gate current to determine the source of the radiation-induced changes. AlGaN/GaN HFETs demonstrated threshold voltage shifts and drain current changes after irradiation. After electron and neutron irradiation applied at ~80 K, measurement of the drain current at this temperature showed an increase that saturated after 10^13 electrons/cm^2 or 10^10 neutrons/cm^2 due to positive charge build-up in the AlGaN layer. Measurement at room temperature after low-temperature irradiation showed a decrease in drain current due to the build up of charged defects along the AlGaN-GaN interface that decrease the mobility in the 2DEG and hence decrease the current. Gate leakage currents increased after low temperature irradiation and the increase was persistent after room temperature annealing. The increased leakage current was attributed to trap-assisted tunneling after application of the trap-assisted tunneling model. Comparison of the model to post-irradiation vs. pre-irradiation data showed that the dominant parameter change causing increased gate current was an increase in trap concentration.
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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.
95 citations
TL;DR: In this article, a trap-assisted tunneling model was used to explain the effect of the degree of nitridation on current enhancement in heavily nitrided films, and the trap density and trap energy level were found to be in the ranges of 1.2×1019-7.2 ×1020 cm−3 and 2.46-2.56 eV, respectively.
Abstract: Conduction enhancement characteristics and the conduction mechanism in nitroxide are reported in this paper. Thermally grown oxides with various thicknesses were nitrided in pure ammonia for different nitridation times. Conduction in thick oxide after short‐time nitridation is dominated by Fowler–Nordheim tunneling with lowered barrier height. A trap‐assisted tunneling model was used to explain the effect of the degree of nitridation on current enhancement in heavily nitrided films. A theoretical calculation was carried out to fit the theory to the experimental results, and the trap density and trap energy level were found to be in the ranges of 1.2×1019–7.2×1020 cm−3 and 2.46–2.56 eV, respectively. These results are explained satisfactorily by the Auger spectroscopic data.
88 citations
TL;DR: In this article, a trap level of 1 eV below the conduction band edge was found for SiO2 at oxide fields 5-7 MV/cm, which is shallower than the ∼2.5 eV trap level reported for nitrogen related traps in thermally nitrided SiO 2.
81 citations
TL;DR: In this paper, a comparison between theoretical calculations of tunneling current and experimental data for the nitrided oxide and SiO2 was made, and it was found that the effective barrier height for electrons at an aluminum-nitrided oxide interface decreases from 3.1 to 2.5 eV for an as-grown nitrin oxide and 2.75eV for a nitrinnealed in O2.
Abstract: Electrical conduction in ultrathin nitrided oxide films on silicon has been investigated by comparing it with that in ultrathin oxide. Significant current enhancement in the nitrided oxide and partial recovery of the enhancement by O2 annealing were observed, which can be satisfactorily explained by a two‐step tunneling via traps generated in the nitrided oxide during nitridation. From the comparison between theoretical calculations of tunneling current and experimental data for the nitrided oxide and the SiO2, it is found that the effective barrier height for electrons at an aluminum‐nitrided oxide interface decreases from 3.1 to 2.5 eV for an as‐grown nitrided oxide and to 2.75 eV for a nitrided oxide annealed in O2. The nitrogen‐related traps are estimated to be situated at the surface portion within 32–34 A from the metal‐insulator interface with the energy level of 2.87 eV for the former and 3.32 eV for the latter below each conduction‐band edge.
79 citations
TL;DR: In this paper, a simplified closed-form trap-assisted tunneling model was employed that produces a fit to the data with a trap depth of 2.1 eV. The difference between this trap model and a model requiring numerical integration was negligibly small (∼2%).
Abstract: Conduction has been studied in ultrathin nitrided oxide, re‐oxidized nitrided oxide, and nitrogen‐annealed nitrided oxide film capacitors in which the nitridation step was performed by a low‐partial‐pressure nitridation technique. Results indicate that, as well as some degree of barrier lowering due to the build‐up of nitrogen at the injecting interface, a trap‐assisted mechanism could be responsible for the enhanced conduction exhibited by the nitrided oxide devices. A simplified closed‐form trap‐assisted tunneling model is employed that produces a fit to the data with a trap depth of 2.1 eV. The difference between this trap model and a model requiring numerical integration was negligibly small (∼2%).
67 citations