Electron emission Si-based resonant-tunneling diode

The quantum mechanical phenomenon of tunneling is of interest from fundamental as well as device points of views. Semiconductor microstructures, and in particular asymmetric double quantum well structures (a-DQWS), provide ideal systems for investigating tunneling phenomena, especially when an electric field is applied to bring various electronic levels into resonance. We first discuss various resonant and nonresonant tunneling processes for electrons and holes, including both coherent and incoherent resonant tunneling and then review recent extensive investigations of resonant and non-resonant tunneling rates of electrons and holes in asymmetric double quantum well structures using time resolved spectroscopy. We also show that cw and ultrashort pulse experiments probe different physics and that it is difficult to obtain quantitative information about resonances and resonant tunneling rates from cw experiments.

Tunnel nanojunctions based on inelastic electron tunneling (IET) have been heralded as a breakthrough for ultra-fast integrated light sources. However, the majority of electrons tend to tunnel through a junction elastically, resulting in weak photon-emission power and limited efficiency, which have hindered their practical applications to date. Resonant tunneling has been proposed as a way to alleviate this limitation, but photon-emissions under resonant tunneling conditions have remained unsatisfactory for practical IET-based light sources due to the inherent contradiction between high photon-emission efficiency and power. In this work, we introduce a novel approach that leverages much stronger resonant tunneling enhancement achieved by multiple metallic quantum wells, which has enabled the internal quantum efficiency to reach ∼1 and photon-emission power to reach ∼0.8 µW/µm2. Furthermore, this method is applicable with different electronic lifetimes ranging from 10 fs to 100 fs simultaneously, bringing practical implementation of IET-based sources one step closer to reality.

In this study, we have applied the numerical simulation and the mathematical analysis to study the resonant tunneling in the case of the existing barriers of electromagnetic material in a superlattice and the effect of the spinning on the energy resonant tunnel. We investigated the tunneling and resonant tunnel in (Ga, Mn)As/GaAs structure of the electron spinning through the superlattice. we found that the levels of resonance are formed inside the barriers and dependence the resonant tunnel for the electron on the spinning up or down of the magnetic materials barriers and lead to the formation of minibands that cause the tunnel phenomenon. We found that symmetry on the long direction of wavefunction growth provides an appropriate wavenumber, as well as the weak coupling between the adjacent wells leading to the formation of so narrow minibands in comparison with the frequency band for the traditional semiconductors. It also turned out that the unit binary class cell specifies the width of the minibands while the potential barriers which depend on spinning lead to the division. In our study, we found that the right choice of the magnetic insulator layers and the layers of the semiconductor enables the lowest minibands to decompose and be divided into two spherical minibands. We Found The maximum transmission coefficient T(E) at energy 0.27 eV for up spin and 0.42eV for a down spin.

A numerical model of a new type of resonant- tunnelling diode based on electron resonant-tunnelling emission from silicon cathode with SiOx-Si multilayer coating has been developed. The model is founded on joint numerical solution of the Schrodinger and Poisson equations system for the time- independent electron wave function, electric field, current and voltage and a small-signal analysis of the last three alternating components. Emitter accumulation layer and contacts presence and an electron delay in a coating quantum well and in a diode transit layer were taken into account. The investigations have shown presence of a negative resistance microwave frequency band for the diode with the electron transit angle from 0 to 2pi/3. The upper frequency of the band is 1012 GHz when resonant tunnelling occurs through the highest resonant level in a quantum well.

The band gap in photonic materials with periodic spatial modulation of refractive index greater than unity can actually be regarded as a potential barrier for photons. Similar to semiconductor quantum well systems due to the electronic band-gap mismatch, a photonic quantum well can be constructed by sandwiching a uniform medium between two photonic barriers. The transmission and reflection coefficients of light through the photonic quantum well are calculated by a modal expansion method with an R-matrix propagation algorithm. Resonance tunneling through the photonic quantum well structure is observed by varying either the well width or the frequency of incident light. Resonance peaks are found within the band-gap region, and indicate the existence of photon virtual states in the well.

In this work, we have investigated magneto-transport and polarization resolved photoluminescence of a GaAs/AlGaAs resonant tunneling diode with Si delta-doping at the center of the quantum well under a magnetic field parallel to the tunnel current. Three resonant peaks were observed in the current-voltage characteristics curve (J(V)) which were associated to donor-assisted resonant tunneling, electron resonant tunneling and to phonon-­assisted resonant tunneling. The optical emission from GaAs contact layers shows evidence of highly spin-polarized two-dimensional electron and hole gases which affect the spin-polarization of carriers in the well. The quantum well photoluminescence shows strong circular polarization degrees with values up to 85% under 15T at the donor assisted resonant tunneling peak voltage. Our results can be exploited for future development of voltage-controlled spintronics devices.

We review our comprehensive investigations of electron and hole tunneling times between quantum wells separated by a single barrier. These studies show strong electronic and phonon resonances, strong influence of collisions and relaxation on tunneling times and provide new insights into nonresonant and resonant tunneling in semiconductor microstructures.

Resonant tunneling(RT) phenomenon in double-barrier(DB) heterostructure[1,2] has a conceptual similarity to a transmission of optical waves in Fabry-Perot (FP) resonator and involves time delay. Its dynamics should be investigated since they limit the ultimate speed of RT devices. Such a study will also clarify similarities and differences between electronic and optical waves. In our previous work[3], we investigated the tunneling escape process of electrons from AlAs/GaAs/AlAs DBRT structures. The measured escape rate was well explained by the idealized theory of FP-like model, which predicts the tunneling escape time τ in DBRT structures is given by |t| 2vk/Lw, when |t|2 ≪1, where t is the transmission coefficient through the barrier, vk is the group velocity of electrons and Lw is the well width. This predicted escape time is equal to the one calculated by the sequential tunneling model, suggesting that the tunneling escape time is not strongly dependent on the coherency of electron waves. This simple relation may not hold for the tunneling process between quantum wells(QW), where resonant coupling effect plays a more sophisticated role. To clarify the resonant tunneling phenomena between QWs, we report, in this paper, our study on electron dynamics in several different double GaAs QW structures separated by thin AlAs barrier, where the coupling condition between QWs was varied by electric fields. Tunneling process was studied at ~20K by measuring time resolved photoluminescence(PL). Picosecond pulses of a mode-locked dye laser were used to generate electron hole pairs in QWs, and the subsequent PL from particular QWs was monitored by a streak camera to determine the time variation of electron density in the QWs. Note that the electrons are lost either by recombination (radiative[4] and nonradiative) and/or by tunneling process. Since the mass of heavy hole is quite heavy, hole tunneling can be neglected at least in the initial phase of tunneling.

Resonant tunneling through one-dimensional quantum-mechanical systems such as multibarrier structures and superlattices has been studied in order to solidify the foundation of exact and comprehensive treatment of it. For general systems with piecewise continuous potential and effective-mass profiles, it is proven that allowable energy levels for resonant tunneling comprise a band structure-i.e., resonance bands which are distinct, in general, from the so-called subbands. One can see a resonance is attained by adjusting external parameters to match with a real resonating pair of the objective section (internal structure). In a series connection of two or more subsections (or a heterostructure with two or more layers), resonant tunneling is shown to be caused, this time, by a matching of generally complex resonating pairs of each couple of succeeding subsections. Two particular kinds of structures, i.e., imaginal-iteration and simple-iteration structures, are investigated in detail with regard to the matching between subsections at each resonant energy level. Thus, the possibility of resonance can be seen not directly related with resonance bands of the subsections. The overall argument will provide insight into the mechanism of resonant tunneling.

The effect of the intense laser field on the electronic states and optical properties of n-type double δ-doped GaAs quantum wells

Thomas–Fermi–Dirac theory of the hole gas of a double p-type δ-doped GaAs quantum wells

The Breit–Wigner formula is exploited to calculate the tunneling transmission probability affected by longitudinal optical phonon scattering in multiple quantum wells composed of Ga1−xAlxAs compounds. A quantitative result shows that the resonance electron energy and the integrated total transmission probability through the potential barriers are not changed, while the transmission peak is reduced and the linewidth is broadened.

Resonant tunneling through a single quantum well of GaAs has been observed. The current singularity and negative resistance region are dramatically improved over previous results, and detecting and mixing have been carried out at frequencies as high as 2.5 THz. Resonant tunneling features are visible in the conductance-voltage curve at room temperature and become quite pronounced in the I-V curves at low temperature. The high-frequency results, measured with far IR lasers, prove that the charge transport is faster than about 10−13 s. It may now be possible to construct practical nonlinear devices using quantum wells at millimeter and submillimeter wavelengths.

An asymmetric double quantum wells (QWs) structure with resonant tunneling is suggested to achieve high efficient four wave mixing (FWM). We analytically demonstrate that the resonant tunneling can induce high efficient mixing wave in such a semiconductor structure with a low light pump wave. In particular, the FWM conversion efficiency can be enhanced dramatically in the vicinity of the center frequency. This interesting scheme may be used to generate coherent long-wavelength radiation in solid-state system.

Sequential resonant and nonresonant tunneling have been investigated in doped GaAs/AlGaAs multiple quantum wells. Negative differential resistance attributable to high field domains expanding through the structure are observed. It is argued that the conductance mechanism is changing with increasing bias, from resonant ground-state tunneling in the low bias regime to nonresonant ground and ground to first exited state in the oscillating differential resistance regime. At higher bias the evolution from nonresonant to resonant tunneling is studied. Calculated tunneling currents are in good agreement with the measured currents both for on and off resonance.