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The authors are grateful for financial support by the state of Bavaria, the German Ministry of Education and Research (BMBF) within the national project HIRT (FKZ 13XP5003B). We present room temperature resonant tunneling of GaSb/AlAsSb double barrier resonant tunneling diodes with pseudomorphically grown prewell emitter structures comprising the ternary compound semiconductors GaInSb and GaAsSb. At room temperature, resonant tunneling is absent for diode structures without prewell emitters. The incorporation of Ga0.84In0.16Sb and GaAs0.05Sb0.95 prewell emitters leads to room temperature resonant tunneling with peak‐to‐valley current ratios of 1.45 and 1.36 , respectively. The room temperature operation is attributed to the enhanced Γ ‐L‐valley energy separation and consequently depopulation of L‐valley states in the conduction band of the ternary compound emitter prewell with respect to bulk GaSb. Postprint

The quantum effects of magnetic flux and in-plane electric field on an electron in a two-dimensional double-barrier nanoring have been studied. It has been found that the electronic structures and the related properties in the ring, such as the polarization, persistent currents, and far-infrared spectroscopy, can be tailored and controlled by the double barriers and the electric field. It may be useful for applications in quantum devices design in the future.

A series array of NbN/TiNx/NbN/TiNx/NbN double-barrier junctions was fabricated on Si wafers, and their current–voltage (I–V) characteristics were measured with and without microwave power in order to investigate their performance for programmable voltage standards. By adjusting the thickness of the TiNx barrier, nearly identical critical currents were obtained for 128 lower and 128 upper junctions in an array. When applying 8 GHz microwave power to an array, a large constant-voltage step (∼3 mA) appeared on the I–V curve. The zero-voltage critical current and the height of the first (n=1) constant-voltage step showed microwave-power dependences coincident with theoretical prediction.

This letter reports the theoretical study of the current–voltage characteristics of the AlAs–GaAs–AlAs double-barrier structure with a thin GaAs well and thin AlAs barriers at room temperature, within a third-neighbor sp3 bond-orbital model. We demonstrate that the tunneling current caused by the L-valley electrons gives a significant contribution to the valley current at room temperature. Moreover, if the AlAs barriers become thick enough (e.g., >3 nm), the tunneling current at room temperature may be dominated by the L electrons instead of Γ electrons.

Transmission zero engineering in lateral double‐barrier resonant tunneling devices is investigated. We show that, by inserting a resonant cavity in the quantum well region of a lateral double‐barrier resonant tunneling structure and engineering the placement of transmission zero‐pole pairs, the current peak‐to‐valley ratio of the device can be drastically improved at low temperature. An advantage of this structure also is that a lower peak voltage can be obtained compared to the corresponding lateral double‐barrier resonant tunneling device.

Dominant photogenerated valley current has been observed in an optically‐excited InGaAs/AlAs double‐barrier resonant‐tunneling diode. The photogenerated valley current in the resonant‐tunneling diode varies with the optical power level. Under intense illumination, the photogenerated valley current increases to such a high level that it becomes dominant over the peak current. As a consequence, the negative differential resistance of the device is removed. The observed photogenerated valley current is described by photogenerating electron‐hole pairs in the depletion region adjacent to the double‐barrier structure. Transient behavior of the photogenerated carriers is also studied. The observed dominant photogenerated valley current may have useful applications.

This letter reports the theoretical study of the current–voltage characteristics of the AlSb–InAs–AlSb double‐barrier structure with a thin InAs well at both 77 and 300 K, within a nearest‐neighbor sp3 bond‐orbital model in which the band‐bending effects are also taken into account. We demonstrate that the tunneling current due to the incident electrons derived from the valence bands gives a significant contribution to the valley and background currents; in addition, it gives the dominant contribution to the valley current when the temperature is low enough.

We report the resonant tunneling of electrons in AlSb‐GaSb‐AlSb and AlSb‐InGaSb‐AlSb double barrier heterostructures grown on different substrate orientations. We have investigated the dependence of the current voltage characteristic on barrier and well thicknesses, as well as on temperature. Resonant tunneling peak to valley (P/V) ratios of 7.6 (GaSb well) and 8.7 (InGaSb well) at 80 K have been obtained. We also report the observation of a second negative differential resistance (NDR) region with an anomalous temperature dependence, and give an experimental estimation of the band alignment in the strained GaSb/InGaSb system based on the variation of the NDR position in the tunneling structures.

This letter reports the study of the resonant‐tunneling characteristics of the AlSb‐InAs‐AlSb double‐barrier structures within a second‐neighbor sp3 bond‐orbital model. The model employs one s‐like antibonding orbital and 3 p‐like bonding orbitals per unit site and is capable of describing the lowest conduction band accurately throughout the entire Brillouin zone. The current‐voltage curve thus obtained, compared to those obtained using the nearest‐neighbor sp3 bond‐orbital model or those obtained from the two‐band model, gives a much better agreement with the experiment.

A current-in-plane tunneling measurement is a superb solution for evaluating a magnetic tunnel junction's properties because it does not require the series of patterning processes in a clean room that have frustrated many researchers because of the damage and side effects frequently induced by these processes. We found that previously proposed current-in-plane tunneling analysis for double-barrier magnetic tunnel junctions (DMTJs) accurately predicts their electrical properties but often fails to provide other detailed properties of DMTJs. Here, we propose and demonstrate a modified analytic method that can provide an excellent estimate of the electrical and magnetic properties of DMTJs by considering the intermediate magnetization state between parallel and antiparallel states, which has previously been ignored. We found that considering this intermediate state is necessary and sufficient for evaluating the tunneling properties. We also prove that our method is valid even for DMTJs with two identical bar...

Defects are often taken as the cause of deviations in the current‐voltage characteristics of heterostructures such as barrier or double barrier, and the so‐called defect‐assisted tunneling effect has been assumed to occur in certain cases. We present an analytical analysis of the tunneling effect which occurs through a barrier and which is assisted by an energy level associated with a defect. Moreover, we show that a negative differential resistance can occur using a single barrier in which a defect is located.

Magnetoquantum oscillations in the tunnel current of a p‐type double‐barrier AlAs/GaAs/AlAs device are used to measure the buildup of hole space charge in the quantum well over a wide range of bias. These measurements demonstrate sequential tunneling of holes. The effective mass for hole tunneling is estimated.

Low frequency noise has been investigated in MgO double-barrier magnetic tunnel junctions (DMTJs) with tunneling magnetoresistance (TMR) ratios up to 250% at room temperature. The noise shows a 1/f frequency spectrum and the minimum of the noise magnitude parameter is 1.2×10−10 μm2 in the parallel state for DMTJs annealed at 375 °C. The bias dependence of noise and TMR suggests that DMTJs with MgO barriers can be useful for magnetic field sensor applications.

Measurements of the current-voltage characteristics of zinc-blende (cubic) Al0.3Ga0.7N/GaN, double barrier resonant tunneling diodes are presented. Clear and reproducible negative differential resistance effects are observed, with room temperature peak-to-valley ratios up to 4 and peak currents up to about 1000 A cm−2.

We report bidirectional direct-current electroluminescence (EL) from i-MgxZn1−xO/n-ZnO/SiOx double-barrier heterostructures on Si. When the heterostructure-based device is forward biased with negative voltage applied on Si, ultraviolet (UV) emission is more intense than visible emissions. The visible emissions appear only at sufficiently high currents. As the device is reverse biased, the visible emissions dominate the EL at low currents. However, they are gradually overridden by the UV emission with increasing current. The EL mechanism has been discussed in terms of energy band structures of the device under forward and reverse biases.

This letter reports a mesopiezoresistive effect in a double-barrier resonant tunneling (DBRT) structure. In a DBRT system, an external mechanical stress causes a tensile strain, and the strain, in turn, affects the resonant tunneling and thereby the resistance. Theoretical analysis was carried out on an AlAs∕GaAs∕AlAs DBRT structure under in-plane uniaxial tensile stresses. The results show that the tunneling current and resistance of a DBRT structure change significantly with external stress-induced tensile strains. The results also show that the resistance-strain response can be tuned effectively by the external voltage. The effect has potential applications in miniature electromechanical devices.

Voltage dependent tunnel magnetoresistance (TMR) has been studied in fully epitaxial (Zn,Co)O∕ZnO∕(Zn,Co)O∕ZnO∕(Zn,Co)O magnetic tunnel junctions (MTJs) with double barrier. The MTJs show extremely small voltage dependence with “half voltage” over 4V above 6K. At 5K, the TMR as a function of voltage is found to be constant up to 2V, and then decreases. “TMR transition” occurs when temperature decreases to 3–4K, and subsequently, the TMR abnormally increases with voltage at 2K. The anomalous voltage dependent TMR is discussed in terms of the large energy separation between the Fermi level and the mobility edge.

I-V characteristics of single electron tunneling from a symmetric and an asymmetric double-barrier tunneling junction (DBTJ) were examined. A single Au nanoparticle was trapped in nanogap whose size was precisely controlled using a combination of electron beam lithography and molecular ruler technique. Though the symmetric junction showed a monotonic rise with a bias beyond the Coulomb gap voltage, the asymmetric junction showed Coulomb staircases. The capacitance of the junction estimated from the fitting curves using the Coulomb conventional theory was consistent with the capacitance calculated from the observed structure. The authors quantitatively found the correlation between the electrical and structural properties of DBTJ.

Double-barrier magnetic tunnel junctions with two MgO barriers and three CoFeB layers exhibiting tunneling magnetoresistance (TMR) values of more than 100% were fabricated. The bias voltage dependence of the TMR ratio is highly asymmetric after annealing at low temperatures, indicating dissimilar CoFeB∕MgO interfaces. The TMR effect decays very slowly for positive bias and is only reduced to half of its maximum value at V1∕2=1.88V when the junctions are processed at 200°C. The largest output voltage, 0.62V, is obtained after annealing at 300°C, a temperature that combines high TMR ratios with a considerable asymmetric bias dependence.

The dependence of current components on GaAs well widths is studied in AlAs/GaAs/AlAs double barrier diode structures having AlAs barriers of 8 atomic layers. It is shown for the first time that the density JRT of resonant current varies from 8×102 to 1.6×104 A cm−2 by the choice of the well width from 9 to 5 nm in accordance with theoretical calculations. Furthermore, one of these diodes shows excellent current‐voltage characteristics at room temperature with a peak to valley ratio of 3, the highest value ever reported.

AlAs‐GaAs‐AlAs double‐barrier resonant tunneling diodes (DBRTDs) with different doping levels in the AlAs layers have been investigated. Two‐step spacer layers were used in all samples. Peak‐to‐valley current ratios (PVCRs) as high as 3.5 (11.3), 3.5 (11.3), and 2.7 (8.2) were observed at 300 K (77 K) for samples with undoped, 1.2×1017 cm−3, and 3×1018 cm−3 doped AlAs barriers, respectively. These results indicate that resonant tunneling is not strongly affected by ionized Si atoms in the AlAs barriers. The excellent PVCRs observed in DBRTDs with two‐step spacer layers is not because of low background impurity densities in the active region, but because of a third barrier formed by band bending in the spacer layers.

Microwave and millimeter‐wave oscillation frequencies and efficiencies of heterojunction double‐barrier resonant‐tunneling structures are investigated theoretically from a time‐dependent point of view. Calculations for two specific devices show that the oscillation characteristics depend strongly on the device parameters, i.e., barrier heights and widths and the well width. Results also show that oscillations in frequencies above limits predicted by a transit tunneling time consideration are less efficient, but not vanishing.

This letter reports the first observation of resonant tunneling negative differential resistance (NDR) through a double barrier GaAs‐AlxGa1−xAs ‐GaAs‐AlxGa1−x As‐GaAs structure at room temperature. The NDR yields radio frequency oscillations at 300 K in a coaxial cable circuit that compare closely to those of a standard 1N3716 tunnel diode.

The influence of external circuit parameters on the measured current‐voltage behavior of double barrier resonant tunneling structures is studied both experimentally and through modeling. It is demonstrated that characteristic ‘‘plateaulike’’ structures, which often appear in the region of negative differential resistance, can be accounted for in terms of the oscillating nature of the circuit, given that only average currents and voltages are monitored.