Tunnel Diode

One of the interesing tunneling phenomena is negative differential resistance (NDR), the basic principle of resonant-tunneling diodes. NDR has been utilized in various semiconductor devices such as frequency multipliers, oscillators, relfection amplifiers, logic switches, and memories. The NDR in graphene has been also reported theoretically as well as experimentally, but should be further studied to fully understand its mechanism, useful for practical device applications. Especially, there has been no observation about light-induced NDR (LNDR) in graphene-related structures despite very few reports on the LNDR in GaAs-based heterostructures. Here, we report first observation of LNDR in graphene/Si quantum dots-embedded SiO2 (SQDs:SiO2) multilayers (MLs) tunneling diodes. The LNDR strongly depends on temperature (T) as well as on SQD size, and the T dependence is consistent with photocurrent (PC)-decay behaviors. With increasing light power, the PC-voltage curves are more structured with peak-to-valley ratios over 2 at room temperature. The physical mechanism of the LNDR, governed by resonant tunneling of charge carriers through the minibands formed across the graphene/SQDs:SiO2 MLs and by their nonresonant phonon-assisted tunneling, is discussed based on theoretical considerations.

Chapter 2 - TUNNELLING IN ESAKI JUNCTIONS

The principle of super-regeneration can be applied to many electronic circuits to achieve large amplifications The advent of the tunnel diode has made available a device which, by virtue of its voltage controlled negative conductance region, can be used as the active element in a simple super-regenerative amplifier. In a tunnel diode super-regenerative amplifier the quenching process, necessary to start and interrupt the oscillations periodically, is simply accomplished by moving the operating point in the current-voltage characteristics from the negative conductance region to the positive conductance region The simplicity of the circuitry associated with the tunnel diode and its low noise capabilities make tunnel diodes super-regenerative amplifiers or detectors very attractive An analysis based on well-established super-regeneration theory shows that tunnel diodes can operate reliably in the super-regenerative mode. The results of the analysis compare with experimental results with good agreement The possibility of utilizing tunnel diode super-regenerative detectors or amplifiers in practical circuitry has boon demonstrated by their incorporation, with good performance, in actual communication circuits.

Simmons tunneling diode model represent a key theoretical framework in the understanding and the modelling of quantum mechanical electron injection from bulk metal into bulk semiconductor, covering both low-voltage direct tunneling and the high-voltage field emission regime [1] . For two-dimensional (2D) semiconductor devices, Simmons model is expected to be invalid due to the reduced dimensionality and the nonparabolic energy dispersion of 2D materials [2] . Particularly, in the device setup of a 2D semiconductor field-effect transistor [3] , the physics of electron laterally injected from the highly-doped metallic 2D source region into the 2D semiconducting channel region remain an open question thus far. In this work, we generalise Simmons 3D tunneling diode model into the case of 2D elecrical contacts. Both parabolic and nonparabolic energy dispersions are considered in our 2D tunneling diode model. The 2D tunneling diode retains the Ohmic linear current-voltage scaling law. However, in the moderate to high voltage regime where field emission process dominates, the current-voltage scaling law exhibits a radical departure from the conventioonal Simmons tunneling diode model. The 2D tunneling diode model represent a quantum extension of the previously developed 2D thermionic injection model [4] and shall provide a theoretical basis for describing the carrier injection phenomena in 2D semiconductor nanochannel tunneling devices.

This paper presents a comparison of tunnel diode to Schottky diode in rectifier at 2.4 GHz under −10dBm input power region. The tunnel diode based rectifier has an advantage of quantum tunneling effect. Therefore it can achieve higher rectification efficiencies. In this work, GI401A tunnel diode and HSMS-285B Schottky diode are used. The input power range of measurements are from −10dBm to − 40dBm. In the same topology, same material, and the same input power situation, the tunnel diode based rectifier achieves 12.6% efficiency, while the Schottky diode based rectifier achieves 6.53% efficiency.

This paper presents results of numerical simulations of a III-V dual-junction solar cell including tunnel diode and Bragg reflector. The simulations are carried out in a commercially available semiconductor simulation environment. For the computation of the quantum efficiency of the subcells a special procedure using biasillumination and bias-voltage is implemented. The model is validated by a comparison of simulated external quantum efficiency (EQE) and IV curve with experimental data. A very good agreement is achieved. Simulations are used to illustrate the influence of the Bragg reflector and the tunnel diode on the EQE. Additionally, the capabilities of the model for design optimization are exemplified by an adaption of the subcells’ thicknesses.

On the theory of hall-effect isolators for tunnel diode amplifiers

In this effort, the authors propose, for the first time, a tunnel diode-based rectifier for 5G/mm-wave energy harvesting. The tunnel diode, a unique semiconductor device with a negative resistance region, is often used in oscillator and amplifier circuits. However, this work exploits one new property for tunnel diodes, that sets a strong foundation for 5G long-range self-powered IoT nodes. This property is verified by the high sensitivity/low turn-on power and self-voltage-regulating behavior of the tunnel diode-based rectifier over a large range of load variations. Compared to a Schottky diode-based rectifier at 28GHz, the tunnel diode counterpart demonstrates a superior compatibility with the ambient mm-wave energy harvesting challenges and needs.

Owing to the similarity of the junction widths and doping levels in epitaxially formed GaAs lasers and conventional tunnel diodes, the gradual degradation of the latter under use might be expected to be intensified in the case of lasers operating under high duty cycle or CW conditions. It was found that the current-voltage characteristics of both the lasers and tunnel diodes underwent considerable thermal degradation even when no bias was applied, and that the degradation was limited to surface or "junction edge" effects. The degradation of the current-voltage characteristic was correlated with degradation in the light output under forward bias. It was concluded that degradation under forward bias was also a surface effect induced by heating rather than by deterioration of the junction in the bulk, as commonly believed. Methods of controlling the degradations are discussed.

Modulation of the current generated by the Na+/K+ pump by membrane potential and protein kinases was investigated in oocytes of Xenopus laevis. In addition to a positive slope region in the current-voltage (I-V) relationship of the Na+/K+ pump, a negative slope region has been described in these cells (Lafaire & Schwarz, 1986) and has been attributed to a voltage-dependent apparent Km value for pump stimulation by external [K+] (Rakowski et al., 1991). To study this feature in more detail, Xenopus oocytes were used for comparative analysis of the negative slope of the I-V relationship of the endogenous Na+/K+ pump and of the Na+/K+ pump of the electric organ of Torpedo californica expressed in the oocytes. The effects of stimulation of protein kinases A and C on the negative slope were also analyzed. To investigate the negative slope over a wide potential range, experiments were performed in Na(+)-free solution and in the presence of high concentrations of Ba2+ and tetraethylammonium, to block all nonpump related K(+)-sensitive currents. Pump currents and pump-mediated fluxes were determined as differences of currents or fluxes in solutions with and without extracellular K+. The voltage dependence of the Km value for stimulation of the Na+/K+ pump by external [K+] shows significant species differences. Over the entire voltage range from -140 to +20 mV, the Km value for the Na+/K+ pump of Torpedo electroplax is substantially higher than for the endogenous pump and exhibits more pronounced voltage dependence. For the Xenopus pump, the voltage dependence can be described by voltage-dependent stimulation by external [K+] and can be interpreted by voltage-dependent K+ binding, assuming that an effective charge between 0.37 and 0.56 of an elementary charge is moved in the electrical field. An analogous evaluation of the voltage dependence of the Torpedo pump requires the assumption of movement of two effective charges of 0.16 and 1.0 of an elementary charge. Application of 1,2-dioctanoyl-sn-glycerol (diC8, 10-50 microM), which is known to stimulate protein kinase C, reduces the maximum activity of the Xenopus pumps in the oocyte membrane by 40% and modulates the voltage dependence of K+ stimulation. For the endogenous Xenopus pump, the apparent effective charge increased from 0.37 to 0.51 of elementary charge and the apparent Km at 0 mV increased from 0.46 to 0.83 mM. For the Torpedo pump, one of the apparent effective charges increased from 1.0 to 2.5 of elementary charge.(ABSTRACT TRUNCATED AT 400 WORDS)

An analysis of the effects of the prostatic hypertropy on he urinary flow in lower-urinary-tract

Little is known about the characteristics of the inwardly rectifying K+ channel (IK1) and the influence of preexisting heart disease on the channel properties in the human heart. We studied the characteristics of cardiac IK1 in freshly isolated adult human atrial and ventricular myocytes by using the patch-clamp technique. Specimens were obtained from the atria and ventricles of 48 patients undergoing cardiac surgery or transplantation and from four explanted donor hearts. The action potential in ventricular myocytes exhibited a longer duration (391.4 +/- 30.2 milliseconds at 90% repolarization, n = 10) than in atrium (289.4 +/- 23.0 milliseconds, n = 18, P < .001) and had a fast late repolarization phase (phase 3). The final phase of repolarization in ventricle was frequency independent. Whole-cell IK1 in ventricle exhibited greater slope conductance (84.0 +/- 7.9 nS at the reversal potential, EK; n = 27) than in atrium (9.7 +/- 1.2 nS at EK; n = 8, P < .001). The steady-state current-voltage (I-V) relation in ventricular IK1 demonstrated inward rectification with a region of negative slope. This negative slope region was not prominent in atrial IK1. The macroscopic currents were blocked by Ba2+ and Cs+. The channel characteristics in ventricular myocytes from patients with congestive heart failure after idiopathic dilated cardiomyopathy (DCM) exhibited distinct properties compared with those from patients with ischemic cardiomyopathy (ICM). The action potential in ventricular myocytes from patients with DCM had a longer duration (490.8 +/- 24.5 milliseconds, n = 11) compared with that for ICM (420.6 +/- 29.6 milliseconds, n = 11, P < .01) and had a slow repolarization phase (phase 3) with a low resting membrane potential. The whole-cell current slope conductance for DCM was smaller (41.2 +/- 9.0 nS at EK, n = 7) than that for ICM (80.7 +/- 17.0 nS, n = 6, P < .05). In single-channel recordings from cell-attached patches, ventricular IK1 channels had characteristics similar to those of atrial IK1; channel openings occurred in long-lasting bursts with similar conductance and gating kinetics. In contrast, the percent of patches in which IK1 channels were found was 34.7% (25 of 72) of patches in atrium and 88.6% (31 of 35) of patches in ventricle. Single IK1 channel activity for DCM exhibited frequent long-lasting bursts separated by brief interburst intervals at every holding voltage with the open probability displaying little voltage sensitivity (approximately 0.6). Channel activity was observed in 56.2% (18 of 32) of patches for DCM and 77.4% (24 of 31) of patches for ICM. Similar results were obtained from atrial IK1 channels for DCM. In addition, channel characteristics were not significantly different between ICM and explanted donor hearts (donors). IK1 channels in cat and guinea pig had characteristics virtually similar to those of humans, with the exception of lower open probability than that in humans. These results suggest that the electrophysiological characteristics of human atrial and ventricular IK1 channels were similar to those of other mammalian hearts, with the possible exception that the channel open probability in humans may be higher, that the whole-cell IK1 density is higher in human ventricle than in atrium, and that IK1 channels in patients with DCM exhibited electrophysiological properties distinct from IK1 channels found in patients with ICM and in donors.

Novel semiconductor struclures with shrinking dimensions and increasing doping result in veiy steep interfaces. The implementation of quantum mechanical effects into the compact model characterizing the current flow is a necessity and considerably contributes to the siniulation of various non-standard effects. Thus the analysis of the dependence of the properties of a tunnel diode on the actual doping profile of the structure is straightfonard. In a tunneling diode with an abrupt doping profile, tunneling through the p+-n' junction is likely to be the dominant mechanism which controls the current flow through the interface. Simulation based on the drift-diffusion approximation is unable to give the corresponding electrical characteristics and results [ 1-71. Various complex analytical models describing the tunneling effect have been developed [8-91 but usually they do not take into account the whole complexity of mutual interactions of different mechanisms of the current flow through the interface. Therefore in our approach the tunneling effect is introduced into the simulator via modification of a general generation-recombination term. The resulting compact formula characterizing the total current flow includes the drift and diffusion, Shockley-Hall-Read generation and recombination, Auger recombination, impact ionization and tunneling as well as the mutual interactions of the mentioned mechanisms of current flow. The properties of the modified simulator were verified by its application to the simulation of the I-V properties of tunnel diodes with different doping profiles and the contribution of the tunneling current to the total current is clearly demonstrated. 2. Theory Adding the tunneling mechanism via an additional generation - recombination term into the current continuity equations modifies the classical drift-diffusion model of the simulation of electrical properties of semiconductor devices. We can then write

A physiologically based multicompartmental computational model of a midbrain dopamine (DA) neuron, calibrated using data from the literature, was developed and used to test the hypothesis that sodium dynamics drive the generation of a slow oscillation postulated to underlie NMDA-evoked bursting activity in a slice preparation. The full compartmental model was reduced to three compartments and ultimately to two variables, while retaining the biophysical interpretation of all parameters. A phase-plane analysis then suggested two mechanisms for the regulation of the firing pattern: (1) bursting activity is favored by manipulations that enhance the region of negative slope in the whole-cell IV curve and inhibited by those manipulations, such as increasing linear currents, that tend to dampen this region and (2) assuming a region of negative slope is present in the IV curve, the bias of the system can be altered, either enabling or disabling bursting. The model provides a coherent framework for interpreting the effects of glutamate, aspartate, NMDA, and GABA agonists and antagonists under current-clamp conditions, as well as the effects of NMDA and barium under voltage-clamp conditions.

We propose a novel negative differential resistance (NDR) device with ultra-high peak-to-valley current ratio (PVCR) by combining pn junction diode with depletion mode nanowire (NW) transistor, which suppress the valley current with transistor off-leakage level. Band-to-band tunneling (BTBT) Esaki diode with degenerately doped pn junction can provide multiple switching behavior having multi-peak and valley currents. These multiple NDR characteristics can be controlled by doping concentration of tunnel diode and threshold voltage of NW transistor. By designing our NDR device, PVCR can be over 104 at low operation voltage of 0.5 V in a single peak and valley current.