Characteristics Of Resonant Tunneling Diodes Research Articles

Physics Based RTD Model Accounting for Space Charge and Phonon Scattering Effects

This paper presents a fully analytical model for the current-voltage (I–V) characteristics of Resonant Tunneling Diodes. Based on Tsu-Esaki formalism, we consider the full electrical potential distribution in the structure, including the space charge regions at the emitter and collector layers. In addition, we account for the scattering suffered by carriers when tunneling through the double-barrier region, as a function of the applied bias voltage. These considerations improve the accuracy of the proposed model when compared with other approaches while keeping it physics based and fully analytical. Finally, the model is validated with experimental and numericaldata, demonstrating its feasibility for applications in circuit simulation environments.

Theoretical investigation into negative differential resistance characteristics of resonant tunneling diodes based on lattice-matched and polarization-matched AlInN/GaN heterostructures

In this work, we report an investigation of resonant tunneling diodes (RTDs) with lattice-matched and polarization-matched AlInN/GaN heterostructures using the numerical simulation. Compared with the lattice-matched AlInN/GaN RTDs, the RTDs based on polarization-matched AlInN/GaN hetero-structures exhibit symmetrical conduction band profiles due to eliminating the polarization charge discontinuity, which achieve the equivalence of double barrier transmission coefficients, thereby the relatively high driving current, the high symmetry of current density, and the high peak-to-valley current ratio (PVCR) under the condition of the positive and the negative sweeping voltages. Simulations show that the peak current density approaches 1.2 × 107 A/cm2 at the bias voltage of 0.72 V and the PVCR approaches 1.37 at both sweeping voltages. It also shows that under the condition of the same shallow energy level, when the trap density reaches 1 × 1019 cm−3, the polarization-matched RTDs still have acceptable negative differential resistance (NDR) characteristics, while the NDR characteristics of lattice-matched RTDs become irregular. After introducing the deeper energy level of 1 eV into the polarization-matched and lattice-matched RTDs, 60 scans are performed under the same trap density. Simulation results show that the degradation of the polarization-matched RTDs is 22%, while lattice-matched RTDs have a degradation of 55%. It can be found that the polarization-matched RTDs have a greater defect tolerance than the lattice-matched RTDs, which is beneficial to the available manufacture of actual terahertz RTD devices.

Influence on Characteristics of RTD Due to Variation of Different Parameters and Material Properties

In this paper, novel features offered by Resonant Tunneling Diode (RTD) are reviewed by simulating it under different conditions. GaAs/AlGaAs based RTD is used as the reference one to obtain the characteristics due to parametric variations. To fulfil this purpose a simple model of resonant electronic transport through a double-barrier structure is developed. I-V characteristics are studied by varying barrier parameters and well width. Different peak and valley currents are measured under these conditions. For the same set of parameters both symmetric and asymmetric cases are considered. Different materials of lower effective mass are also taken into consideration to improve Peak to Valley Ratio (PVR). The Indium (In) based materials are considered to compare the characteristics obtained from the conventional GaAs based RTD structure. All these proposed structures are simulated using Silvaco Atlas software.

Quantum Transport Simulation of Nanowire Resonant Tunneling Diodes Based on a Wigner Function Model With Spatially Dependent Effective Masses

We present a self-consistent and three-dimensional quantum simulation for nanowire resonant tunneling diodes (RTDs) based on the Wigner transport equation with spatially dependent effective masses (SDEM), which is discretized by a third-order upwind difference scheme for high-accuracy calculation. Our calculation shows that the current density/voltage ( $J\text{--}V$ ) characteristics of nanowire RTDs with a radius ( $R$ ) $ 5 nm largely deviate from those of the one-dimensional RTDs. As $R$ decreases below 5 nm, the peak-to-valley ratio (PVR) of the low- $V$ negative differential resistance (NDR) decreases rapidly, and the high- $V$ NDR peak shifts sensitively to lower $V$ and becomes sharper. In this study, these results are shown to be closely related to the SDEM. According to our analysis, the SDEM along the transport direction contributes to the formation of an ‘effective double barrier’ in the energy subbands that is higher than the double barrier expected by the band offset, and the SDEM along the confinement direction reduces the height of the effective double barrier. The performance of nanowire RTDs with $R 5 nm was proven to be highly dependent on $R$ because of the SDEM along the confinement direction.

Atomic-scale Authentication with Resonant Tunneling Diodes

ABSTRACTThe room temperature electronic characteristics of resonant tunneling diodes (RTDs) containing AlAs/InGaAs quantum wells are studied. Differences in the peak current and voltages, associated with device-to-device variations in the structure and width of the quantum well are analyzed. A method to use these differences between devices is introduced and shown to uniquely identify each of the individual devices under test. This investigation shows that quantum confinement in RTDs allows them to operate as physical unclonable functions.

Theoretical analysis of external feedback effect on oscillation characteristics of resonant-tunneling-diode terahertz oscillators

The resonant tunneling diode (RTD) is a candidate for a compact and coherent source in the terahertz frequency range. We show theoretically that the oscillation characteristics of RTDs are strongly affected by the external feedback of partially reflected output power. The oscillation frequency and output power largely change with a small amount of the reflected output power as a periodic function of the position of the reflection object. A change in the current–voltage curve, which can be used for the detection of the external feedback, also occurs.

Simulation of electron transport in metal/high-k-oxide/SiO2/p+Si resonant-tunneling diodes

Operation of a metal–nanometer-thick insulator–semiconductor (MIS) structure on p+Si substrate as a resonant-tunneling diode (RTD) is considered. RT electron transport occurs between the p+Si valence band and the metal via the sub-bands in the conduction band within the near-interface quantum well in a regime of steady non-equilibrium depletion. The performed modeling reveals some possibilities for improvement and adjustment of the RTD characteristics by using multi-layered high-k-oxide/SiO2 stacks instead of a single SiO2 film. The main results of a high-k layer addition are the more expressive RT-related features due to suppression of a low-energetic non-resonant electron tunneling transport.

Resonant tunneling of interacting electrons in an AC electric field

The problem of the effect of electron-electron interaction on the static and dynamic properties of a double-barrier nanostructure (resonant tunneling diode (RTD)) is studied in terms of a coherent tunneling model, which includes a set of Schrodinger and Poisson equations with open boundary conditions. Explicit analytical expressions are derived for dc and ac potentials and reduced (active and reactive) currents in the quasi-classical approximation over a wide frequency range. These expressions are used to analyze the frequency characteristics of RTD. It is shown that the interaction can radically change the form of these expressions, especially in the case of a hysteretic I-V characteristic. In this case, the active current and the ac potentials can increase sharply at both low and high frequencies. For this increase to occur, it is necessary to meet quantum regime conditions and to choose a proper working point in the I-V characteristic of RTD. The possibility of appearance of specific plasma oscillations, which can improve the high-frequency characteristics of RTD, is predicted. It is found that the active current can be comparable with the resonant dc current of RTD.

Quantitative analysis of the trapping effect on terahertz AlGaN/GaN resonant tunneling diode

We report on a simulation for terahertz aluminum gallium nitride (AlGaN)/gallium nitride (GaN) resonant tunneling diode (RTD) at room temperature by introducing deep-level defects into the polarized AlGaN/GaN/AlGaN quantum well. Results show that an evident degradation in negative-differential-resistance characteristic of RTD occurs when the defect density is higher than ∼106 cm−2, which is consistent with the measurements of the state-of-the-art GaN RTDs. At around 300 GHz, the simulation for a RTD oscillator also demonstrates evident decreases of rf power and efficiency because of the electron trapping effect.

Negative differential resistance in bilayer graphene nanoribbons

Lack of a bandgap is one of the significant challenges for application of graphene as the active element of an electronic device. A bandgap can be induced in bilayer graphene by application of a potential difference between the two layers. The simplest geometry for creating such a potential difference is two overlayed graphene nanoribbons independently contacted. Calculations, based on density functional theory and the nonequilibrium Green’s function formalism, show that transmission through such a structure is a strong function of applied bias. The simulated current voltage characteristics mimic the characteristics of resonant tunneling diode featuring negative differential resistance.

The Design and Testing of Mesopiezoresistive Effect Electromagnetic Driven Micromachined Gyroscope

Resonant tunneling diode (RTD) is a bipolar negative resistance device with the features of high speed, high frequency, low voltage and power, has been proved to have mesopiezoresistive effect, and the current-voltage characteristics of RTD is a function of stress. In the paper, the mesopiezoresistive effect of resonant tunneling diodes and Coriollis effect are both used in the research of gyroscope, so a novel gyroscope structure is proposed. The feasible fabrication process is designed according to present process technology, and the gyroscope is fabricated by GaAs surface micromachining processes and bulk micromachining technology. By the driven experiment it is verify that the gyroscope can be successfully driven. And the range of fabricated gyroscope natural frequency is also obtained, which is larger than 4KHz.

Demonstration of negative differential resistance in GaN/AlN resonant tunneling diodes at room temperature

GaN/AlN resonant tunneling diodes (RTD) were grown by metal-organic chemical vapor deposition (MOCVD) and negative differential resistance with peak-to-valley ratios as high as 2.15 at room temperature was demonstrated. Effect of material quality on RTDs’ performance was investigated by growing RTD structures on AlN, GaN, and lateral epitaxial overgrowth GaN templates. Our results reveal that negative differential resistance characteristics of RTDs are very sensitive to material quality (such as surface roughness) and MOCVD is a suitable technique for III-nitride-based quantum devices.

Effects of series and parallel resistances on the current-voltage characteristics of small-area air-bridge resonant tunneling diode

We have studied experimentally and theoretically the effects of series and parallel resistances on the current-voltage (I-V) characteristics of the resonant tunneling diode (RTD) in the format of a small-area freestanding air bridge. It has been shown by standard quantum mechanical considerations that the I-V characteristics consists of a simple resonant current peak (without bistability) and the voltage at the current peak is quite low, whereas experiments show not only a much high current-peak voltage, but also the bistability. Furthermore, experimental peak-to-valley ratio is in general quite low. By analyzing material and device structures, it has been demonstrated that the series resistance in the RTD contacts shifts the peak in current to higher voltage, it also creates the experimentally observed bistability effect in the region of the tunneling resonance. The parallel resistance induces a leakage current and reduces the peak-to-valley ratio. We have further performed similar analyses to many RTD structures reported in the literature and the conclusions remain the same.

Capacitance–voltage characteristics and switching time of double barrier resonant tunneling diode fabricated with epi-Si and γ-Al2O3

Capacitance-voltage and conductance-voltage characteristics of resonant tunneling diodes fabricated with epitaxial Si/γ-Al2O3 heterostructure have been studied at room temperature. The capacitance-voltage characteristics of this structure show a large capacitance peak near the resonant tunneling bias. This capacitance peak is considered as quantum capacitance originated from the charge storage in the quantum well of the structure during tunneling process. Capacitance-voltage characteristics also were studied at different frequencies to understand the charge storage mechanism in the resonant tunneling diode structure. Resonant tunneling diodes with different barrier thicknesses were studied and tremendous improvement in the NDR characteristics was observed. A maximum peak-to-valley current ratio of 248 was obtained at room temperature. Using this capacitance value switching time and maximum operational frequency of the RTD structure were determined.

The resonant tunneling of holes through double-barrier structures with InAs QDs at the center of a GaAs quantum well

The effect of InAs quantum dots (QDs) grown in the center of a GaAs quantum well on the tunneling characteristics of resonant-tunneling diodes based on p-AlAs/GaAs/AlAs heterostructures is studied. The introduction of QDs results in a shift and broadening of resonance peaks in the current-voltage characteristics of the diodes; however, this effect is found to be strongly dependent on the number of the 2D subband involved in the tunneling. The obtained dependence is attributed to origination of the fluctuation potential in the vicinity of the QD layer.

Experimental verification on the origin of plateau-like current–voltage characteristics of resonant tunneling diodes

Current-voltage (I–V) characteristics of GaAs-based resonant tunneling diodes have been investigated in the presence of a perpendicular magnetic field. Electron resonant tunneling is strongly suppressed by the applied magnetic field, leading to peak current decreasing with increasing magnetic field. The observed plateau-like structures appear in negative differential resistance region on the I–V curves and are magnetic-field dependent. The plateau-like structures are due to the coupling between the energy levels in the emitter well and in the main quantum well.

Resonant tunneling characteristics in SiO2/Si double-barrier structures in a wide range of applied voltage

We have found that current–voltage characteristics of resonant tunneling diodes (RTDs) with a structure of Al/upper-SiO2/p−-Si-well/lower-SiO2/n+-Si substrate are distinctly categorized by the kinetic energy of electrons in the Si well injected from the n+-Si substrate. For RTDs with a lower-SiO2-layer thickness below 4 nm, negative differential conductance is observed in accordance with our previous work [Y. Ishikawa, T. Ishihara, M. Iwasaki, and M. Tabe, Electron. Lett. 37, 1200 (2001)], where electrons have relatively low kinetic energies below 2.7 eV in the Si well. On the other hand, RTDs with a lower-SiO2 layer thicker than 5 nm have specific characteristics of a large current peak and a large hysteresis at higher kinetic energies above 2.9 eV, indicating that hot electrons are readily stored in the Si well, probably due to enhanced impact ionization scattering.

SPIN FILTERING IN MAGNETIC HETEROSTRUCTURES

Several techniques were proposed to achieve solid state spin filtering such as magnetic tunnel junctions comprised of half-metallic compounds or solid state Stern-Gerlach apparatus. Another alternative consists in using spin-dependent resonant tunneling through magnetically active quantum wells. Recent advances in molecular beam epitaxial growth made it possible to fabricate exotic heterostructures comprised of magnetic films or buried layers (ErAs, GaxMn1-xAs) integrated with conventional semiconductors (GaAs) and to explore quantum transport in these heterostructures. It is particularly interesting to study spin-dependent resonant tunneling in double-barrier resonant tunneling diodes (RTD) with magnetic elements such as GaAs/AlAs/ErAs/AlAs/ErAs/AlAs/GaAs, GaxMn1-xAs/AlAs/GaAs/AlAs/GaAs, and GaAs/AlAs/GaxMn1-xAs/AlAs/GaAs. We present the results of our theoretical studies and computer simulations of transmission coefficients and current-voltage characteristics of resonant tunneling diodes based on these double-barrier structures. Resonant tunneling of holes (GaxMn1-xAs-based RTDs) is considered. Our approach is based on k·p perturbation theory with exchange splitting effects taken into account. We analyze exchange splitting of different resonant channels as a function of magnetization as well as spin polarization of the transmitted current as a function of bias. We found that resonant tunneling I – V characteristics of the double-barrier magnetic hererostructures strongly depend on the doping level in the emitter as well as on the orientation of the magnetization.

Effect of Si/Si1-yCy/Si Barriers on the Characteristics of Si1-xGex/Si Resonant Tunneling Structures

P-type double barrier resonant tunneling diodes (RTD) with the single Si0.6Ge0.4 quantum well and double Si0.6Ge0.4 spacer have been realized by using an ultra clean low-pressure chemical vapor deposition system. The effect of Si1-yCy layer on the characteristics of the devices was shown by comparing the current-voltage (I-V) characteristics of RTD's of the barriers of Si layers with that of Si/Si1-yCy/Si structures. The peak voltage was gradually increased and the resonant current decreased obviously with increasing C content in the Si/Si1-yCy/Si barriers. The origin of the phenomena above can be attributed to the C related deep acceptor levels in the Si/Si1-yCy/Si barriers. The possible mechanism for the observed I-V characteristics was shown more clearly by increasing C content to 3% and changing the thicknesses of Si and Si1-yCy layers in the Si/Si1-yCy/Si barriers.

Resonant-tunneling-diode relaxation oscillator

Monolithic resonant-tunneling-diode (RTD) relaxation oscillators are fabricated. The highest repetition rate of this pulse generator is 6.7 GHz with a pulse width of approximately 60 ps. Oscillators with an RTD connected to an off-chip transmission line have been operated at a rate as low as 34 MHz while maintaining a similar pulse width. Characterization aided with simulations provides a better understanding of the RTD relaxation oscillator and the effects of the RTD characteristics on the performance of the oscillator.