Resonant Interband Tunneling Structure Research Articles

Well-defined electrical properties of high-strain resonant interband tunneling structure

The GaAs/InAs high-strain resonant interband tunneling diodes (HSRITDs) have been implemented by metal organic chemical vapor deposition (MOCVD). The current–voltage characteristics of variable quantum well and barrier thickness grown on (1 1 1) GaAs substrates are investigated. Experimental results reveal that the quantum barrier and well layer will influence current–voltage properties such as the peak current density, valley current density, and peak-to-valley current ratio (PVCR). Both peak current and valley current density decrease with increasing layers width. This result also exhibits the variation of PVCR with layers width.

Multi-band Wigner function formulation of quantum transport

A Wigner function representation of multi-band quantum transport theory is developed in this Letter. The equations are derived using non-equilibrium Green's function formulation with the generalized Kadanoff–Baym ansatz and the multi-band k.p Hamiltonian including spin. The results are applied to a two-band resonant inter-band tunneling structure.

Multi-band Wigner function formulation of quantum transport

A Wigner function representation of multi-band quantum transport theory is developed in this Letter. The equations are derived using non-equilibrium Green's function formulation with the generalized Kadanoff–Baym ansatz and the multi-band k.p Hamiltonian including spin. The results are applied to a two-band resonant inter-band tunneling structure.

Time‐Domain Analysis of One‐Dimensional Quantum‐Mechanical Waves Using Bergeron Equivalent Circuits

AbstractElectron wave devices making use of the wave nature of the electron have been studied extensively. It is important to systematically understand and use the wave phenomena in a potential structure as the operating principle of these devices. In this paper, a method based on Bergeron equivalent circuits is proposed as a technique for time domain analysis of the electron wave propagation expressed by the one‐dimensional quantum‐mechanical wave equation. It is shown that by this technique the time domain analysis of the wave behavior described by the Schrödinger equation under the effective mass approximation and the two‐ and three‐band model equations can be systematically treated by nodal analysis, including boundary conditions. Also, as a boundary condition of an open system that is important in time domain analysis, an absorbing boundary condition due to a potential structure with loss is proposed. By means of the proposed technique, the time domain analysis of the incident wave packet on a GaAs/AlAs structure considering Γ − X mixing, and on a resonant interband tunneling structure is carried out and its behavior is described. © 2001 Scripta Technica, Electron Comm Jpn Pt 2, 85(1): 1–12, 2002.

Equivalent circuit representation for resonant interband tunneling structures

Electron wave devices that use quantum-mechanical waves have been actively researched. It is important to understand and to use wave phenomena in potential structures because they are the operational basis of devices. Recently, some circuit-theoretical approaches have been proposed for analyzing and designing wave phenomena in potential structures. In this paper, equivalent circuits based on two- and three-band models that describe wave phenomena in potential structures composed of various semiconductor materials are proposed. By using the proposed equivalent circuits, wave phenomena in resonant interband tunneling (RIT) structures are formulated in terms of equivalent circuits. To confirm the validity of this method, resonant tunneling phenomena are analyzed. Circuit functions and matrices, especially the impedance concept, can be effectively used for analyzing and designing wave phenomena in RIT structures. © 1998 Scripta Technica, Electron Comm Jpn Pt 2, 81(9): 1–10, 1998

Analysis of resonant tunneling using the equivalent transmission-line model

Presents a simple general and exact method for solving resonant tunneling problems in multilayered heterostructures. This method is based on the analogy of wave propagation between the transmission line and the potential structure. By using the proposed method, it is shown that electron wave propagation can be treated as wave propagation on an equivalent circuit and that various problems can be systematically solved by using well-developed circuit functions and circuit matrixes. In particular, our equivalent circuit can be effectively used for analysis of resonant interband tunneling (RIT) structures and resonant tunneling structures including /spl Gamma/-X mixing by using the interface matrix. Various properties of the resonant tunneling structure and a guideline for designing new quantum effect devices can be easily obtained. In order to show the validity and usefulness of this method, some numerical examples of InAs-GaSb and GaAs-AlAs potential barrier structures are presented.

Magnetotunneling in interband tunnel structures

We examine the effect of in-plane magnetic fields on transport properties of InAs/GaSb/AlSb-based resonant interband tunneling (RIT) structures and barrierless resonant interband tunneling structures using the multiband k\ensuremath{\cdot}p quantum transmitting boundary method [Y. X. Liu et al., Phys. Rev. B 54, 5765 (1996)]. In interband tunnel structures with GaSb quantum wells, the primary peak found in the current-voltage characteristic is due to the coupling of InAs conduction-band electrons to quantized GaSb light-hole states, and a weaker shoulder peak typically shows up as the result of coupling to quantized GaSb heavy-hole states. We find that in-plane magnetic fields can enhance this electron-heavy-hole coupling, resulting in a more pronounced shoulder peak in the current-voltage characteristic. Qualitative agreement between our calculations and experimental data on RIT structures offers strong evidence for hole-mixing induced electron-heavy-hole coupling in interband tunnel structures.

Tunneling spectroscopy of resonant interband tunneling structures

We report the first study of a resonant interband tunneling (RIT) structure using tunneling spectroscopy. Peaks in the tunneling spectra are shown to correspond to energies of acoustic phonons in the constituent materials of the RIT. We conclude that these phonons are involved in inelastic tunneling through the structure and could play a role in determining the overall form of the current-voltage characteristic.

InAs/AlSb/GaSb resonant interband tunneling diodes and Au-on-InAs/AlSb-superlattice Schottky diodes for logic circuits

Integrated resonant interband tunneling (RIT) and Schottky diode structures, based on the InAs/GaSb/AlSb heterostructure system, are demonstrated for the first time. The RIT diodes are advantageous for logic circuits due to the relatively low bias voltages (/spl sim/100 mV) required to attain peak current densities in the mid-10/sup 4/ A/cm/sup 2/ range. The use of n-type InAs/AlSb superlattices for the semiconducting side of Schottky barrier devices provides a means for tailoring the barrier height for a given circuit architecture. The monolithically integrated RIT/Schottky structure is suitable for fabrication of a complete diode logic family (AND, OR, XOR, INV).

The study of [formula omitted] δ-doping resonant interband tunneling diode

The δ-doping InGaAs GaAs quantum well resonant interband tunneling diode by low pressure metal organic chemical vapor deposition has been successfully grown. The full width at half maximum of the doping profile analyzed by capacitance-voltage measurement is small. Two kinds of δ-doping resonant interband tunneling diodes were simulated in this study. One was the δn + -i-δp + resonant interband tunneling structure and the other was the δn + -i-δp + -i-δn + single barrier resonant interband tunneling structure. The simulated current-voltage characteristics exhibited the expected N-shaped negative differential resistance. The calculated peak-to-valley current ratio (PVCR) values of δn + -i-δp + and δn + -i-δp + -i-δp + structures are 6 and 5.6, respectively. The calculated PVCR value is larger than experimental PVCR values for the δn + -i-δp + structure. The PVCR values of this study are better than the published data of other authors.

Investigation of resonant interband tunneling structures using a three-band [formula omitted] model

A three-band k · p model (CLH model) considering realistically the coupling effects among the conduction band, light-hole band and heavy-hole band is proposed to investigate further the characteristics of the resonant interband tunneling structures. The tunneling current densities for k ‖-independent and -dependent cases are calculated for comparison. It is found that the inclusion of the k ‖ dependence is important in the discussion of the current-voltage (I–V) characteristics. The small peaks in low temperature I–V characteristics for GaSb/AlSb/InAs/GaSb/AlSb/InAs broken-gap interband tunneling (BGIT) structure with a 120 Å wide InAs well is owing to the substantial coupling between conduction band and heavy-hole band on nonzero k ‖. The effects coming from the k ‖ dependence also contribute to the rising of the first peak and the broading of the second peak in the low temperature I–V characteristics for BGIT structure with a 240 Å wide InAs well. A CLH model can interpret the particular phenomena in the I–V characteristics that cannot be explained by the two-band model, usually used in the investigation of the interband tunneling structures.

Compositional and structural analysis of AlSb(As) tunneling barriers in InAs/AlSb(As)/GaSb resonant interband-tunneling structures

InAs/AlSb/GaSb/AlSb/InAs interband-tunneling structures have been analyzed with respect to the composition and structural quality of the AlSb tunneling barriers. The addition of AlAs monolayers at the interfaces between the AlSb barriers and the InAs and GaSb layers was found to result in the expected reduction in the valley current density of the resonant interband-tunneling diode. Vibrational mode Raman spectroscopy showed that the introduction of AlAs monolayers led to the formation of pseudoternary Al(SbAs) barriers, which cause the observed reduction of the valley current density. Ellipsometric measurements indicate that the structural quality of both types of barrier layers, with and without AlAs monolayers added to the interfaces, is inferior to that of thick bulklike AlSb layers. The observation of Raman scattering from a coupled hole plasmon-phonon mode indicates the formation of a hole gas in the GaSb quantum well at the center of the tunneling structure.

Effects of carrier mass differences on the I–V characteristics of resonant interband tunneling structures in the presence of parallel magnetic field

We investigate the effect of differences between the quantum well and the electrode carrier effective masses on the current–voltage characteristics of double-barrier interband tunneling structures under an applied magnetic field parallel to the current. The system is described by a two-band tight-binding Hamiltonian that incorporates electron and light-hole interaction and the current is calculated using the Keldysh nonequilibrium Green’s-function diagrammatic technique. The formalism is applied to InAs/AlSb/GaSb double-barrier structures considering either the InAs or the GaSb as the quantum well. The behavior of the I–V characteristics as a function of the magnetic-field strength is strongly influenced by the mass differences and opposite curvatures of the conduction and the valence bands. The features we obtain are quite different for InAs and GaSb. They are both also different from the more traditional magneto-tunneling results for GaAs/AlGaAs, where the electrodes and the quantum well electronic masses are equal. The behavior of the I–V characteristics with the applied magnetic field is in good qualitative agreement with available experimental data.

Phonon-assisted transmission in resonant interband tunneling devices

We demonstrate that phonon-assisted transmission may play a considerably lower role in interband tunneling structures than in intraband tunneling based devices as a result of the symmetry difference between electron and hole states. An example of current–voltage characteristics is calculated for resonant interband tunneling structure with confined electron and hole states.

Proposal of interband tunneling structures with strained layers

A type of interband tunneling structure with strained layers is proposed. InxGa1−xSb/ InxAl1−xSb/InAs/InxAl1−xSb/InxGa1−xSb strained resonant interband tunneling structures are theoretically studied by calculating current-voltage characteristics using realistic band structure and making comparisons to analogous unstrained structures. The results show that the interband tunneling windows of strained structures can be expanded by the introduction of strain in the InAs quantum-well layer. With a wider interband tunneling window, the peak current density is enhanced due to the broader tunneling transmission spectrum and higher bias required for resonant interband tunneling. The peak current density is also examined as a function of InAs well width for different InAlSb barrier widths.

InAs/antimonide-based resonant tunneling structures with ternary alloy layers

We have studied two modifications of mixed arsenide/antimonide resonant tunneling structures, in which one of the binary components is replaced by a ternary alloy. The first structure is based on an InAs/AlSb/GaSb resonant interband tunneling structure with the GaSb quantum well layer replaced by a GaAs x Sb 1 − x alloy layer. The added As decreases the lattice constant in the well, and the resulting strain can shift the heavy hole subbands below the incoming electron energy. We find that the negative resistance effect can be enhanced by properly adjusting the splitting via the As concentration. A maximum enhancement in the peak-to-valley ratio was obtained with a 10% As concentration in the diodes we fabricated. The second structure is a modification of a conventional InAs/AlSb double barrier structure, in which the AlSb barriers are replaced by Al x Ga 1 − x Sb with x ≈ 0.5. In these structures, the pronounced type II band alignment results in an entirely new type of current vs voltage characteristic exhibiting intrinsic current bistability (double-valued currents for a given voltage) instead of the conventional voltage bistability. Peak-to-valley voltage ratios as high as 1.5 have been observed with current densities in the 10 5 A/cm 2 range.

The effect of the InAs layer thickness on the peak current density and subband properties of the GaSb/InAs/GaSb/AlSb/InAs structures

The incorporation of the InAs layer as the blocking layer into the GaSb side of the GaSb/AlSb/InAs single-barrier interband tunneling structure resulting in a GaSb/InAs/GaSb/AlSb/InAs resonant interband tunneling structure has been proven to greatly enhance negative differential resistance peak-to-valley current ratios and peak current density. The role of the InAs layer induced electron and light hole coupling related to the device performance is then investigated. A three-band model, incorporating the coupling effect of the spin-orbit split-off hole band, is employed to probe the effect of the InAs layer thickness on the peak current densities and the subband properties of the GaSb/InAs/GaSb/AlSb/InAs resonant interband tunneling structures. The calculated peak current densities are in reasonable agreement with the experimental data reported previously. The transmission coefficients based on the three-band calculation can be used to interpret the variations of the peak current densities well. In addition, the ‘‘repulsion’’ of the conduction subbands in the InAs well and light-hole subbands in the GaSb well is observed for larger InAs layer thickness. A ‘‘transition energy region’’ resulting from the crossing of the respective subbands in the InAs and GaSb wells is also observed. The effect of the InAs layer induced subband properties related to the carrier transport in the peak current of the GaSb/InAs/GaSb/AlSb/InAs structure is also discussed.

Investigation of time-dependent resonant interband tunneling

We present a time-dependent calculation of InAs/AlSb/GaSb/AlSb/InAs and InAs/GaSb/InAs resonant interband tunneling structures. We follow the propagation of electron wave packets through the systems and determine the temporal behavior of the device operation by calculating various time scales. We compare these time scales with the lifetime of the corresponding quasi-bound state computed from both the static transmission curve and the exact solution of the quasi-bound state.

An energy- and spatial-dependent effective mass approach for resonant interband tunneling devices

A theoretical study of resonant interband tunneling in GaAs δ-doped inducing homostructure and polytype GaSb/AlSb/InAs heterostructure is presented in this article. The resonant interband tunneling in such homo- and heterostructures is modeled by an energy- and spatial-dependent effective mass equation incorporating the general transfer matrix method. The present formalism is based on the envelope function approximation as done to date, but contains two significant improvements: a more realistic treatment of the spatial and energy dependence of effective-mass and bandstructures; and the avoidance of plane-wave, Airy function or Wentzel–Kramers–Brillouin approximations for calculating the envelope function in favor of direct numerical evaluation. The transmission coefficients of the unipolar and bipolar resonant interband tunneling structures are calculated and the symmetric and asymmetric multiple quantum well resonant interband tunneling structures are also discussed.

Improvement of peak-to-valley ratio by the incorporation of the InAs layer into the GaSb/AlSb/GaSb/AlSb/InAs double barrier resonant interband tunneling structure

InAs blocking layer is incorporated into the GaSb/AlSb/GaSb/AlSb/InAs double barrier resonant interband tunneling structure to improve the peak-to-valley ratios. It is found the ratio rises to 21 at room temperature and the peak current density keeps nearly constant for InAs layer reaches 30 A and then both of them decreases with the increase of InAs thickness. However, while the InAs blocking layer further increases to 240 A, the I-V characteristic shows multiple negative differential resistance behavior. These interesting phenomena can be modeled to be due to the coupling effect of InAs blocking layer and GaSb well layer.