Triple-barrier Resonant Tunneling Diodes Research Articles

Hole-tunneling Si0.82Ge0.18/Si triple-barrier resonant tunneling diodes with high peak current of 297 kA/cm2 fabricated by sputter epitaxy

Hole-tunneling Si0.82Ge0.18/Si asymmetric triple-barrier (TB) resonant tunneling diodes (p-RTDs) were created by sputter epitaxy instead of conventional chemical vapor phase epitaxy. As a result, a peak current density (PCD) of 297 kA/cm2 with a peak-to-valley current ratio of 7.3 was recorded at room temperature. The observed high planarity of the films grown by sputter epitaxy is also considered one of the factors behind the high PCD. From the results of self-consistent theoretical calculations of current–voltage characteristics using box-shaped potentials as a first approximation and considering space charge effects of quantum wells, heavy-hole-to-heavy-hole and light-hole-to-light-hole state transitions under the tunneling conditions of the TB potential structure applied in this study were found to be inherent current paths. Moreover, the light and heavy hole currents contribute almost equally to the overall device current, resulting in a theoretical PCD of 637 kA/cm2, which is close to the experimental result. Further analytical simulations with adjusted series resistance and thickness of the nondoped layer allowed the alignment of the theoretically obtained PCD voltage position with the experimentally obtained one. Thus, the theoretical and analytical calculations explain the operation mechanisms of SiGe/Si p-RTDs, and the proposed fabrication method using our sputter epitaxy method is very useful for the actual production of high-PCD SiGe/Si p-RTDs operating at room temperature.

Admittance Spectroscopy Up to 67 GHz in InGaAs/InAlAs Triple-Barrier Resonant Tunneling Diodes

Admittance Spectroscopy Up to 67 GHz in InGaAs/InAlAs Triple-Barrier Resonant Tunneling Diodes

Theoretical study of electronic properties of resonant tunneling diodes based on double and triple AlGaAs barriers

In this paper, we investigated the effect of the central AlGaAs barrier width Lb2 in a resonant tunneling diode (RTD) composed by triple barriers on the current-voltage characteristics, and electronic density of free carriers. In addition, this is a comparative study on the current-voltage characteristics that are produced by a double-barriers and triple-barriers RTD. Our simulation was performed using a non-equilibrium Green’s formalism (NEGF). The results showed that the double-barrier RTD produced a higher current density than the triple-barrier RTD. However, in the triple-barrier RTD, the maximum current was obtained for lower applied bias compared to the double-barrier RTD. The peak to valley current ratio (PVCR) has been evaluated and our results indicate that the double-barrier RTD can produces a higher ratio values compared to those produced by triple-barrier RTD. Our findings also showed that for the triple-barrier RTD, the negative differential resistance (NDR) depended on the width Lb2 of the central barrier. By reducing Lb2, the NDR decreased dramatically and disappeared completely for Lb2 = 3 nm. These results open the door for designing a double and triple-barrier RTD with suitable negative differential resistances. The RTD simulation was performed using the Nanohub tool, which confirms the various results presented in this paper.

Numerical simulation of triple-barrier resonant tunneling diodes based on graphene

Numerical simulation of triple-barrier resonant tunneling diodes based on graphene

Electrical characterization of triple barrier GaAs/AlGaAs RTD with dependence of operating temperature and barrier lengths

In this article, we present a model of Triple barrier Resonant tunneling diodes (TBRTDs) and characterize its electrical properties and their dependence of operating temperature and barrier length associated with varying structural parameters of the device. This paper also demonstrates the potential impact of doping concentration on current density of the device. Furthermore, Local density of states (LDOS) and transmission coefficient at various operating temperatures are analysed. Quantum tunneling mechanism results, based on Landauer-Buttiker formalization of non-equilibrium Green's function within ballistic limits, shows high peak current with 2nm triple barrier structure and achieve high peak to valley ratio as compared to other barrier structure. Significantly, comparison helps in analyzing the better device between the proposed device structures. Simulation of the device has been performed with the use of Nextnano3 tool which confirms the various results presented in this research.

Planar electron-tunneling Si/Si0.7Ge0.3 triple-barrier resonant tunneling diode formed on undoped strain-relaxed buffer with flat surface

We demonstrated a planar electron-tunneling Si/Si0.7Ge0.3 triple-barrier (TB) resonant tunneling diode (RTD) formed via a channel layer on an undoped strain-relaxed quadruple-Si1−xGex-layer (QL) buffer. Compared with a conventional vertical Si/Si0.7Ge0.3 TB RTD formed on a heavily doped QL buffer, the dislocation density is low, the surface is flat, and the resonance current density is much larger. These observations, together with analyses of current–voltage (I–V) curve fitting to the physics-based analytical expression, suggest that the enhanced I–V characteristics in the planar RTD are related to decreases in the number of crystalline defect states and the structural and potential fluctuations.

Tuning of terahertz intrinsic oscillations in asymmetric triple-barrier resonant tunneling diodes

Intrinsic terahertz oscillations of the electronic current in the asymmetric triple-barrier resonant tunneling diode are investigated by means of the time-dependent Wigner-Poisson method. The current-voltage characteristics calculated for the nanodevice exhibits four separate bias voltage windows with the current oscillations, which are caused by two different mechanisms. One of these bias voltage windows, for which the electronic current oscillations stem from the negative feedback between the electronic current and the coupled quasi-bound states in the quantum wells embedded in the active region of the nanodevice, is considered in detail. It is demonstrated that the amplitude and frequency of the current oscillations in this bias voltage window depend on the coupling between the quasi-bound states formed in the quantum wells. Strength of this coupling is controlled by the thickness of the central barrier separating the quantum wells, which allows to tune the amplitude and frequency of the terahertz oscillations. Additionally, it was shown that the amplitude of the current oscillations can be tuned by shifting up or down the energy of the bottom of the wider quantum well. These properties suggest that the considered nanodevice may be of interest because of its possible application as tunable terahertz generator.

Time-Domain Analysis of Large-Signal-Based Nonlinear Models for a Resonant Tunneling Diode with an Integrated Antenna

Large-signal-based nonlinear models are developed to analyze a variety of dynamic performances in a resonant tunneling diode (RTD) with peripheral circuits such as an integrated broad band bow-tie antenna, a bias circuit and a bias stabilizer circuit. Dynamic modes of the RTD are classified by the time-domain analysis with the model. On the basis of our model, we suggest a possibility to discuss a terahertz order oscillation mode control, and the ASK modulation in several tens Gbit/sec in the RTD with the broad band antenna. Validity of the model and analysis is shown by explaining measured results of modulated oscillation signals in fabricated triple-barrier RTDs.

Analysis of a monolithic integrated rectenna by using an InGaAs/InAlAs triple‐barrier resonant tunneling diode for zero bias detection of submilimeter‐waves

AbstractZero bias millimeter‐wave detection has been investigated by using backward diodes with InGaAs‐based or Sb‐based interband tunneling and Schottky contact InGaAs‐ based double‐barrier resonant tunneling diodes (DBRTDs). These were intended to be typical cases where the antenna and the detector are individually designed and mutually connected. On the other hand, in this paper we focus on constructing a monolithic type of rectenna (rectifying antenna) for sub‐millimeter wave detection. Our objective is to propose and analyze zero bias detection properties with an InGaAs/InAlAs triple‐barrier resonant tunneling diode (TBRTD) integrated with a bow‐tie type of broadband self‐complementary antenna. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Equivalent Circuit Model of Triple-Barrier Resonant Tunneling Diodes Monolithically Integrated with Bow-Tie Antennas and Analysis of Rectification Properties towards Ultra Wideband Terahertz Detections

Towards an application for terahertz detector, a monolithic integrated device structure of a triple-barrier resonant tunneling diodes (TBRTDs) with a bow-tie antenna is proposed and its terahertz rectification properties are investigated on the basis of a physics-based equivalent circuit model. A possibility of zero-bias detection is examined owing to nonlinear asymmetric current–voltage characteristics. A possibility of broadband zero-bias detection in terahertz range is suggested for a tentatively designed device structure. A method to analyze rectified signal is established taking the self-bias effect into account.

Equivalent Circuit Model of Triple-Barrier Resonant Tunneling Diodes Monolithically Integrated with Bow-Tie Antennas and Analysis of Rectification Properties towards Ultra Wideband Terahertz Detections

Towards an application for terahertz detector, a monolithic integrated device structure of a triple-barrier resonant tunneling diodes (TBRTDs) with a bow-tie antenna is proposed and its terahertz rectification properties are investigated on the basis of a physics-based equivalent circuit model. A possibility of zero-bias detection is examined owing to nonlinear asymmetric current–voltage characteristics. A possibility of broadband zero-bias detection in terahertz range is suggested for a tentatively designed device structure. A method to analyze rectified signal is established taking the self-bias effect into account.

Subterahertz oscillations from triple-barrier resonant tunneling diodes with integrated patch antennas

We report on subterahertz oscillations of resonant tunneling diode oscillators with an integrated patch antenna. The device consists of an InGaAs/InAlAs triple-barrier resonant tunneling diode and a patch antenna on an InP substrate. Current-voltage characteristics indicate a peak current density of 280 kA/cm2, with a peak-valley ratio of about 3 at room temperature. An oscillation frequency of 517 GHz was observed at room temperature through Fourier transformed infrared spectroscopy. The results agree with electromagnetic analysis.

Implementation of Physics-Based Model for Current-Voltage Characteristics in Resonant Tunneling Diodes by Using the Voigt Function

We derive physics-based formula of current-voltage characteristic for resonant tunneling diodes (RTDs) by using the Voigt function. The Voigt function describes the mixing condition of homogeneous and inhomogeneous broadenings of peak energy width in transmission probability, which is sensitively reflected to nonlinear negative differential resistance of RTDs. The obtained formula is applicable to the SPICE model of RTD without performing numerical integrals. We indicate validity of the formula by comparing to measured data for double-barrier and triple-barrier RTDs.

Spin selector by ferroelectric triple barrier resonant tunneling diode

We propose a spin selector of ferroelectric triple barrier resonant tunneling diode with diluted magnetic quantum wells. Spin transport properties of this spin selector are investigated by nonequilibrium Green’s function method. Results show the oscillation of spin polarization of current occurred at low bias voltage due to a transmission resonant peak splitting into subpeaks. By reversing the electric dipole direction of ferroelectric barriers, the spin direction of polarized current is reversed simultaneously at a fixed bias voltage. This implies that the spin direction of injected current can be selected through this spin selector without changing the applied magnetic field.

Reduced Phonon Scattering in an Asymmetric Triple Barrier Resonant-Tunneling Diode at High Magnetic Fields

The relaxation of hot electrons injected by resonant tunneling into a wide undoped drift region is investigated by measuring the field dependence of the I – V characteristics. In the resonant tunneling region, an increase of the current up to 10% and a decrease in the peak voltage of the resonant tunneling characteristics are observed for a field parallel to the current. It is demonstrated that both phenomena result from a magnetic field induced phonon bottleneck effect in the drift region. In high-field regions, phonon scattering of hot electrons is reduced due to strong confinement into quasi-one-dimension states. However, at magneto-resonance fields, strong current minima are observed.

Characterization of Argon Fast Atom Beam Source and Application to Mesa Etching Process for GaInP/GaAs Triple-Barrier Resonant Tunneling Diodes

Towards an application for the mesa etching process of semiconductor quantum devices, a saddle-field argon fast atom beam (FAB) source was characterized in terms of energy distribution spectra for residual ions and neutralization coefficient under various process conditions. The neutralization coefficient was evaluated to be in the order of 90% and slightly depended on operating parameters. It was confirmed that a small discharge current and a small discharge voltage contribute to obtaining a high neutralization efficiency. Argon FAB etching was performed to form a mesa structure of GaInP/GaAs triple-barrier resonant tunneling diodes (TBRTDs), and clear negative differential resistance characteristics were obtained with high yields. The FAB etching process also contributes to obtaining a low measured peak voltage in TBRTDs as compared with the case of wet etching.

Shot-noise characteristics of triple-barrier resonant-tunneling diodes

We have found experimentally that the shot noise in InAlAs-InGaAs-InAlAs Triple-Barrier Resonant-Tunneling Diodes (TBRTD) is reduced over the 2eI Poissonian value whenever their differential conductance is positive, and is enhanced over 2eI when the differential conductance is negative. This behavior, although qualitatively similar to that found in double-barrier diodes, differs from it in important details. In TBRTDs the noise reduction is considerably larger than predicted by a semi-classical model, and the enhancement does not correlate with the strength of the negative differential conductance. These results suggest an incomplete understanding of the noise properties of multiple-barrier heterostructures.

Novel Magnetic Random Access Memory Cell Consisting of Magnetic Tunnel Junction Connected in Parallel with Negative Differential Resistance Device

A novel magnetic random access memory (MRAM) cell consisting of a magnetic tunnel junction (MTJ) and negative differential resistance (NDR) device connected in parallel is described. The NDR characteristics are used to increase the effective magnetoresistance (MR) ratio of the MTJ. Circuit simulations were performed for the memory cell with a triple-barrier resonant-tunneling diode (RTD) to confirm the efficacy of the basic operation. Furthermore, a hybrid circuit built from the CoFe-based MTJ and GaAs-based interband tunnel diode was fabricated. The circuit showed that the effective MR ratio was enhanced almost tenfold from its original value of 11% to 103%.

Fabrication and characterization of GaInP/GaAs triple barrier resonant tunneling diodes grown by MOCVD

GaInP/GaAs triple barrier resonant tunneling diodes (TBRTDs) grown by metal organic chemical vapor deposition were fabricated. Temperature dependence of current–voltage characteristics was measured from 18.6 to 294.1 K and negative differential resistance was observed up to 167 K. From the temperature dependence of peak voltage, peak current, valley voltage, and valley current, we estimated that the NDR characteristic of the TBRTDs is due to alignment and misalignment of quantum levels of left and right well at energy close to the conduction band bottom.

Theoretical analysis of resonant tunneling in triple‐barrier structures under electric fields

AbstractAssuming a practical device application of resonant tunneling in a triple‐barrier structure, equations for theoretical analysis of the tunneling transmission coefficient and the resonance condition are derived with regard to the tunneling phenomena in asymmetric triple‐barrier structures in the presence of an applied bias. From the numerical analysis results, an interesting phenomenon not observed in structures with two or fewer barriers is found. As the bias voltage is increased, the transmission peak value of the resonant spectrum, which initially decreases, begins to increase again and several peaks with a spectral value of 1 (unity resonance) appear. At that time, the resonance condition is studied. Further, the effect of the tunneling transmission characteristics of triple‐barrier structures on the voltage–current relationship in a triple‐barrier resonant tunneling diode is studied. By means of the equations derived here, the resonant bias voltage in the triple‐barrier structure can be determined. The conclusions derived in this paper are considered useful for the design of resonant tunneling devices using triple‐barrier structures. © 2002 Wiley Periodicals, Inc. Electron Comm Jpn Pt 2, 85(12): 10–19, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjb.10075