Double-barrier Tunneling Diodes Research Articles

Design of Solar Blind Photodetectors for Communication with Green Signal (λ= 0.532µm) in Space. Part II

The areas of Free Space Optical (FSO) communication and high-speed Visible Light Communication (VLC) offer potential for very high-speed data transmission. Favorable attributes including high frequency and wider bandwidths that can enable transmission speeds of the order 100Gb/s, associated with the visible region of the electromagnetic spectrum make it preferable for allowing communication among satellites and ground stations, under-water communication, etc. However, limitations associated with spectral absorption characteristics of the propagating media have stymied further development of such technologies.
 Aims: Commercial lasers operating in red, green and blue lights combined with three photodetectors, each sensitive to selected wavelengths (colors) present basics of long-distance optical communication system. The current study (Part II) depicts the design and operation of a solar-blind photodetector capable to work explicitly with green wavelength of 532nm.
 Study Design and Results: The structure of the solar-blind photodetector consists of two sections made of InxGa1-xN (Indium Gallium Nitride) heterostructure, (where x denotes the mole fraction)-a filter and a double barrier tunneling diode. The topmost approximately 1µm thick section acts as a filter and as a p-i-n solar cell providing the required voltage bias to the photodiode. The filter with Eg (Energy Band Gap)=2.33eV absorbs all photons having wavelengths shorter than 532nm. The double barrier tunneling photodiode which comprises the lower section operates with Eg=2.28eV. It consists of an n-type lightly doped quantum well having a width of 2.5nm housed between two lightly doped barriers of 10nm thickness. The 0.12µm topmost and bottom regions of the photodiode are doped with p and n (2×105cm-3) type impurities, respectively. The illuminated cross-section area of the device is finalized at 1mm2.

Analysis of single- and double-barrier tunneling diode structures using ultrathin CaF2/CdF2/Si multilayered heterostructures grown on Si

The current–voltage (I–V) characteristics of single-barrier and double-barrier tunneling diode structures using CaF2/CdF2/Si ultrathin multilayered heterostructures grown on Si substrates have been theoretically analyzed and their material parameters, such as the conduction band discontinuity (ΔEC) at the heterointerface and effective mass (m*), have been evaluated by fitting simulation with the measured I–V characteristics. ΔEC between the ultrathin (1–3 nm) CaF2 and Si layers and m* for CaF2 were found to be 1.5–2.3 eV and 0.3–1.0m0, respectively. A clear thickness dependence of these parameters was observed, and the deviations of m* and ΔEC were approximately 30–50%, which probably originated from the thin layer thicknesses in atomic order. Using the estimated values derived from the single-barrier tunneling diodes, m* for CdF2 was also estimated to be 0.36m0 by fitting simulation of double-barrier diodes. These results will contribute to clarifying the design principle of tunneling devices with CaF2 and enhancing quantitative studies on electron transport in atomically thin multilayered heterostructures.

DESIGN & OPTIMIZATION OF AN I-RTD HYBRID THz OSCILLATOR BASED UPON In1−xGaxAs/GaSbyAs1−y HETEROSTRUCTURE SYSTEMS

An In 1− x Ga x As / GaSb y As 1− y hetero-system with staggered band-lineups as solid-state platform for design of an interband resonant double-barrier tunneling diode (I-RTD) based optically-pulsed (OT) hybrid device for generating THz oscillations is theoretically investigated. It is demonstrated that this optical I-RTD hybrid is compatible with the robust state-of-art 1.55 micron laser technology Multi-band wave equations in the framework of six-band Kane's model are applied for understanding the carrier dynamics when strain-induced effects are present. Simulation results for practical circuit implementations clearly show the superiority of this new oscillator concept.

Electron transport within resonant tunneling diodes with staggered-bandgap heterostructures

The electron transport physics within the conduction-band of resonant tunneling diodes with staggered-bandgap structure is analyzed. Here, the current–voltage characteristic for AlGaSb/InAs/AlGaSb double-barrier tunneling diodes is calculated in the framework of the six-band Kane model. This work demonstrates that the conduction-band electron transport is extremely dependent on the coupling between the conduction and valence bands and that an accurate estimate of current density requires the application of a multi-band model. In addition, the application of a multi-band model yields results that are in excellent agreement with existing experimental measurements on staggered-bandgap structures when well known material parameters are utilized.

A light-induced tunneling state in a submicron double barrier tunneling diode with a center-doped well

We will present the observation of a light-induced meta-stable impurity state in a submicron center-doped double barrier tunneling diode (DBRTD) manufactured by a novel single-step e-beam lithography process in which no further alignment for the interconnect between the bonding pad and the small active device region is required. We attribute the meta-stable tunneling state, which can be switched by light and high voltage bias, to the light- or field-induced charge redistribution in the active tunneling region.

I-V characteristics by radial tunneling in double-barrier tunneling diodes with cylindrical barriers

Radial tunneling transport in a double-barrier tunneling diode (DBTD) with cylindrical barriers has been theoretically studied. Calculations use a generalization of the transfer matrix method. Fine oscillation is demonstrated in transmission spectra and I-V characteristics. It is attributed to the coherence of traveling waves associated with cylindrical geometry. Various Al/sub x/Ga/sub 1-x/As-GaAs DBTD's with cylindrical barriers have been examined at absolute zero and room temperatures. Results are compared with DBTD's with planar geometry. It is recognized that different bias direction induces asymmetric I-V characteristics. Devices that operate on this inborn asymmetry are proposed. The device characteristics could be less sensitive to temperature than that of planar structures due to the fundamental operation principle. The results are useful to understand charge transport by the fast tunneling in quantum-well and superlattice structures with different geometries.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Photon-assisted transmission through an oscillating quantum well: A transfer-matrix approach to coherent destruction of tunneling.

Based on a trasfer-matrix formalism, photon-assisted tunneling is studied in a strongly driven double-barrier tunneling diode. Two scenarios are considered: A driving potential ${\mathit{V}}_{1}$cos(\ensuremath{\omega}t) acting on the central quantum well, which may be realized with electrostatic gates close to the quantum well, and a driving electric field across the diode generated by a laser field. Strong quenching of the transmission probability is found for certain parameters {${\mathit{V}}_{1}$,\ensuremath{\omega}} of the driving field, which can be explained in terms of zeros of fractional Bessel functions, ${\mathit{J}}_{\ifmmode\pm\else\textpm\fi{}\ensuremath{\nu}}$(\ensuremath{\gamma}${\mathit{V}}_{1}$/\ensuremath{\Elzxh}\ensuremath{\omega}), where \ensuremath{\gamma} is a structural parameter. The effect shows a strong similarity to the ``coherent destruction of tunneling'' recently found in strongly driven quartic double wells.

The effect of growth temperature on AlAs/GaAs resonant tunnelling diodes

In this paper we report on a systematic investigation of the influence of the growth temperature on the current voltage (I-V) characteristics of symmetric AlAs/GaAs double-barrier tunnelling diodes grown by molecular beam epitaxy (MBE) and a correlation between electrical and structural properties. It is shown by high-resolution transmission electron microscopy (HRTEM) that the growth temperature affects the interface roughness and the symmetry of the double-barrier region. Both the microstructure of the interfaces and the Si doping spreading in the double-barrier region have a significant influence on the peak-to-valley ratio (PVR) and the symmetry of the I-V characteristic. The substrate temperature was varied from 480 to 680 degrees C. It is demonstrated that the highest PVRS at room temperature are found for samples grown in the temperature range 580-600 degrees C.

Calculation of the wave functions in the space charge region of a double-barrier resonant tunneling diode, with applications

In a bound potential well wave functions can exist only for the eigen states. However, nonzero wave functions would exist for all the energies inside a potential well with totally reflecting barrier on one side and partially transmissive barrier on the other side. A model is presented to calculate wave functions inside such a potential well. A similar situation is encountered in the triangular well developed in the space charge region of the emitter of a double-barrier tunnel diode. This paper shows that a significant amplitude of the wavefunction exists inside the well for energies far-off the resonant energies. Existence of these wave functions significantly influences the current of the potential structure. The model is then applied to calculate the current in a double-barrier potential structure incorporating inelastic scattering. Results show very good qualitative agreement with the reported measured results.

Optical investigation of tunneling in AlAs/GaAs/AlAs double-barrier diodes.

We describe time-integrated and time-resolved photoluminescence measurements made on a series of n-type symmetric and asymmetric AlAs/GaAs/AlAs double-barrier tunneling diodes. Optical measurements of the electron charge buildup in the well near the peak in the tunneling current are used to deduce the average dwell time. This is found to be shorter than expected for tunneling through a Γ-point AlAs collector barrier for barriers thicker than about 3 nm but can be explained if there is strong scattering into X-point valleys. Under high-intensity illumination rue also observe a substantial photoexcited hole current with clear tunneling peaks together with accumulation near the collector barrier and in the well

A novel GaAs delta-doping induced triangle-like double-barrier tunneling diode

On presente une diode a double barriere a puits quantiques (DBQW) avec un puits non dope en AsGa entre 2 barrieres en forme de triangle a dopage delta. Les caracteristiques I-V montrent la resistance negative differentielle (NDR) type n obtenue a faible polarisation ainsi que la NDR type S obtenue a forte polarisation

Modeling of the I–V characteristics of single and double barrier tunneling diodes using A k · p band model

We model the I–V characteristics of single and double barrier tunneling diodes using the complex band structure of the tunneling barrier obtained from a k · p band model. Band-bending is calculated by solving two coupled 1-D Poisson's equations with a classical potential in the accumulation region. The transfer matrix method is used for the calculation of the transmission probability of the tunneling electron whose complex k-vector is obtained from the band structure. An energy dependent density of states effective mass which is also calculated from the band structure is used. I–V characteristics for In 0.53Ga 0.47As/In 0.52Al 0.48As/In 0.53Ga 0.47As single and double barrier tunneling diodes obtained from this model agree quantitatively with experiment.

Resonant injection quantum well diodes and lasers

Simple modifications of the standard GaAsGaAlAs double barrier tunneling diode and quantum well laser structures are considered. Calculations show that by replacing the outer GaAs layers of the diode by small aluminum concentration GaAlAs, the peak-to-valley ratio of the negative resistance can be increased. A similar structure is formed if thin high aluminum content barriers are added on one or both sides of the quantum well in a quantum well laser. The barriers then create a resonance in the well region. The alloy concentration outside of the barriers can be chosen to line up the incoming electron energy with the resonance, creating a greatly enhanced charge density in the well. Electrons are thereby captured by the well more efficiently and threshold currents may be lowered.