Calculated Tunneling Currents Research Articles

Comparison of Simulation and Measurement of Gate Leakage Current in Metal/Al<sub>2</sub>O<sub>3</sub>/GaN/AlGaN/AlN/GaN Capacitors

We compare the simulations and measurements of gate leakage current in metal-insulator-semiconductor capacitors fabricated on standard AlGaN/GaN transistor layers. In the simulations, a fixed charge density at the interface between the Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> layer and the GaN cap layer was assumed for simplicity. The fixed charge layer (which depends on bias and device history) was obtained from capacitance-voltage measurements. The calculated tunneling current due to field emission from localized states in the GaN cap layer agreed with the experimental results. No additional leakage mechanisms had to be invoked.

Analysis of electron direct tunneling current through very-thin gate oxides in MOS capacitors with the parallel-perpendicular kinetic energy components and anisotropic masses

An electron direct tunneling current model of n+- poly - Si/SiO2/p - Si(100) metal-oxide-semiconductor (MOS) capacitors has been developed by considering a parallel-perpendicular kinetic energy coupling, which is represented by the gate electron phase velocity, and anisotropic masses under a parabolic E-k dispersion relationship. The electron effective mass in the oxide and the electron phase velocity in the n+ poly-Si gate are the only two fitting parameters to compare calculated tunneling currents to measured ones. It was obtained that the calculated tunneling currents fit well to the measured ones. The electron effective mass in the oxide layer tends to increase with decreasing the oxide thickness. In addition, the gate electron velocity is a constant of 1x105m/s. Moreover, the theoretical model offers a simple treatment and an accurate result in obtaining the tunneling current.

Electron and hole components of tunneling currents through an interfacial oxide-high-k gate stack in metal-oxide-semiconductor capacitors

Two different components of tunneling current in the TiN/HfSiOxN/SiO2/p-Si(100) metal-oxide-semiconductor capacitor have been presented. The tunneling currents were calculated by taking into account a longitudinal-transverse kinetic energy coupling. The calculated tunneling currents were compared with that measured ones by employing the electron and hole effective masses and phase velocities as fitting parameters. It has been shown that hole tunneling currents dominate at low voltages whereas at high voltages the tunneling currents are mainly contributed by electrons. It has also been found that the effective mass of hole in the HfSiOxN layer is higher than that of electron. The gate electron and substrate hole velocities are 1×105 m/s independent of the HfSiOxN thickness. In addition, it is speculated that the electron and hole effective masses in the HfSiOxN layer perhaps increase as its thickness decreases.

Modeling of temperature dependence of the leakage current through a hafnium silicate gate dielectric in a MOS device

The coupling between the longitudinal and transverse components of the electron thermal motion due to the difference between the effective electron mass of the hafnium silicate and silicon can explain the temperature dependence of the tunneling current through the hafnium silicate gate dielectric. By taking this coupling effect into consideration, the calculated tunneling currents under different temperatures fit well with the experimental data. The numerical calculations demonstrate that the temperature dependence of the tunneling current strongly depends on the thickness of the hafnium silicate gate dielectric. By comparing the results of the coupling effect on the tunneling current through the hafnium silicate film with those of the silicon dioxide layer, the coupling effect has been found to be more important for the case of hafnium silicate than that for the case of silicon dioxide.

Effects of inelastic scattering on interband tunneling in GaSb/AlSb/InAs/GaSb/AlSb/lnAs broken-gap interband tunneling structures

Effects of inelastic scattering on interband tunneling in GaSb/AlSb/InAs/GaSb/AlSb/InAs BGIT's are investigated. The broadening mechanisms due to inelastic scattering are incorporated into the interband tunneling theory. The transmission and reflection coefficients are calculated with the aid of a three-band model, in which the conduction, light-hole, and split-off bands are coupled with one another. It is found that the inelastic scattering lowers the transmission peak and broadens the full-width at half-maximum, resulting in the decrease of the tunneling current. The calculated tunneling current due to inelastic scattering is found to have better agreement with the experiments. In addition, as the valley current plays an important role in the peak-to-valley current ratio (PVR), we then try to deduce the origin of the valley currents. The thermionic current is included in the valley current to estimate the peak-to-valley current ratio. The thermionic component from the GaSb well has important contribution to the valley current in the studied structures. The peak-to-valley current ratio is also estimated and found to have better agreement with the experiment when the inelastic scattering is considered.

Trapping effects in HgCdTe

Carrier trapping influences the performance of HgCdTe infrared detectors in the 8–12 μm range by enhancing tunneling currents, reducing excess carrier lifetimes, and increasing g–r and 1/f noise. In this work, the effects of carrier trapping on the tunneling currents in n+p diodes are calculated, and the dependence of the tunneling current on temperature, bias, doping level, and trap characteristics is illustrated. It is shown that by assuming the dominant trap energy to be at the Fermi level, the calculated tunneling currents exhibit many of the peculiar features which have been observed experimentally. The related effects that minority carrier traps have on the excess carrier lifetimes are also discussed, and a simple method of estimating many of the relevant trapping characteristics from lifetime measurements is presented.

Sequential resonant and nonresonant tunneling in GaAs/AlGaAs multiple quantum wells

Sequential resonant and nonresonant tunneling have been investigated in doped GaAs/AlGaAs multiple quantum wells. Negative differential resistance attributable to high field domains expanding through the structure are observed. It is argued that the conductance mechanism is changing with increasing bias, from resonant ground-state tunneling in the low bias regime to nonresonant ground and ground to first exited state in the oscillating differential resistance regime. At higher bias the evolution from nonresonant to resonant tunneling is studied. Calculated tunneling currents are in good agreement with the measured currents both for on and off resonance.

Tunneling currents in reverse biased Hg1− xCdxTe photodiodes

A first-order, one-dimensional model for calculating bulk interband tunneling currents in reverse-biased abrupt n + p Hg 1− x Cd x Te photodiodes is presented. The tunneling probability as a function of the electron energy E is shown to be: T = exp{−√ 2m∗ h 2 √ 2ϵ 0ϵ s q 2N A E G[(1− E E G )( π 2 −sin −1√ −E E G−E )−√ −E E G ]},where E G is the bandgap, N A and ϵ S are the doping and dielectric constant of the substrate, respectively, and m∗ is the effective mass as in Kane's k·p model. The current, calculated by integrating the flux of the depletion region electrons incident on the barrier which are candidates for the tunneling process, times the tunneling probability (the value of the wavevector at the classical turning point being calculated from the non-parabolic band equation at k $ ̃ - 0) is: I A = caseq 4hπ 2 E Gk BT P 2∫ 0 −E max T( E 2 )dE,where k B is the Boltzmann's constant, P is the momentum matrix element and E max = − qV R + E; F, p − E v, p . The calculated tunneling currents are an excellent fit with measured reverse-bias current-voltage characteristics of diodes with minimized surface effects, without the need for fitting parameters.