Bistability in the current–voltage characteristics of semiconductor superlattices and quantum cascade laser structures has the potential for wide-ranging applications, particularly in sensing systems. However, the interdependency of applied bias and current injection in conventional two-terminal structures has led to complications in analysis and rendered the bistability phenomenon difficult to implement in practical applications. Here, we report a new kind of electronic bistability coupled to optical switching in a resonant tunneling bipolar superlattice transistor. This bistability manifests as sharp discontinuities in the collector current with extremely small variations of the applied voltage, which arise from unstable tunneling transmission across the hetero-barrier between the two-dimensional electron gas (2DEG) at the edge of the transistor base and the collector superlattice structure. The electronic transitions between high and low quantum mechanical transmissions are demonstrated to be caused by self-consistent variations of the internal electric field at the heterointerface between the 2DEG and the superlattice. They are also present in the base current of the three-terminal device and result in sharp switching of near-infrared spontaneous light emission output from an interband radiative recombination process with a peak emission wavelength of 1.58 μm. A comprehensive quantum mechanical theoretical model accounting for the self-consistent bistable tunneling transmission is in quantitative agreement with the experimental data. The measured peak transconductance sensitivity value of 6000 mS can be used in the highly sensitive detector and non-linear device applications.

An overview of the electronic and optical properties of the various types of quantum dots (QD) made of solid-state materials is presented. Whereas they share common physical characteristics such as small sizes and the ability to contain and manipulate few particles, QD's exhibit fundamental specificity in the manifestation of electron charge, spin, or single photon emission, each with their respective potential technological applications. In this context, five types of solid state QD's i.e. Planar QD's, Vertical QD's, Self-Assembled QD's, Silicon Nanocrystals, and Colloidal QD's are addressed with their own physical properties. Comprehensive modeling techniques suited for each type of QD are briefly mentioned.

Janus MoSSe sub-nm pore exhibits polarity-driven ion adsorption and charge-induced transport dynamics, yielding asymmetrical I – V curves, with potential nanofluidics applications.

We investigate ion-electron Coulomb drag in 2D nanofluidic slits using a generic physical model based on the Boltzmann transport formalism. The emphasis is placed on the fluid, oxide, and semiconductor dielectric constants as well as on the geometry and oxide thickness to maximize the electronic drag current and power output. Our model confirms electronic drag current amplification predicted in silicon nanochannels and shows that optimum amplification is achieved for an oxide dielectric constant equal to the geometric mean of the fluid and semiconductor constants, as well as with thin oxide layers while maintaining high surface carrier concentrations in semiconducting layers surrounding the 2D nanoslit. Our analysis, which provides guidelines for 2D slit design optimization, also shows that nanoslits made of 2D materials like graphene combined with thin oxide and optimized dielectric constants enhance drag current amplification over conventional Si/SiO2 nanochannels.

We provide an analysis of nonlinear transport in diamond and cubic GaN (c-GaN) with emphasis on the different types of optical phonon scattering i.e., optical deformation potential (ODP) scattering versus polar optic phonon (POP) scattering limiting the carrier velocity. Both types of carrier mobilities and carrier saturation (peak) velocities in diamond and c-GaN as functions of different doping types and concentrations are obtained by directly solving the Boltzmann equation. Our model indicates that the nonrandomizing nature of POP scattering causes carrier temperature cooling, resulting in higher carrier drift velocity than with ODP scattering. This effect, in addition to the small carrier effective masses and large optical phonon energies, is responsible for the higher peak velocities in c-GaN, compared to carrier drift velocity in diamond.

We model a GaAs quasi-one-dimensional quantum wire in an applied longitudinal field and focus on mechanisms of electron emission leading to real-space transfer from the wire. The Monte Carlo simulation assumes an initial electron distribution in the wire and calculates the time required for electrons to undergo nonequivalent intervalley scattering to three-dimensional states. The model includes multiple subbands, polar optic and acoustic phonons, intervalley scattering, and band-structure nonparabolicity. Results have been obtained for different confinement conditions as well as different temperatures. We find that the required time is a very strong function of the longitudinal field and ranges from 4 ns down to 1 ps for fields in the range of 100 V/cm to 8 kV/cm. The corresponding distances in the wire vary from 130 \ensuremath{\mu}m down to the submicrometer range.

Ionic transport through a graphene biomimetic subnanometer (sub-nm) pore of arbitrary shape and realistically decorated by intrinsic negatively charged sites is investigated by all-atom molecular dynamics (MD) simulations. In the presence of external electric fields, cation trapping-assisted translocation occurs in the vicinity of the 2D subnanometer pore, while the anion current is blocked by the negative charges. The adsorbed cations in such asymmetrically charged nanopores are located on the top of the nanopore instead of blocking the pore, as suggested previously in highly symmetric pores such as crown ethers. Our analysis of the different types of energy involved in ion translocations indicates that electrostatics is the dominant factor controlling ion transfer across these sub-nm pores. A physical model based on the thermionic emission formalism to account for the free energy barriers to ion flow reproduces the I-V characteristics.

In this chapter, we provide a detailed description of a comprehensive computational approach for simulating biomolecules translocating through an electrically active solid-state nanopore. Emphasis is placed on bio-detection via in-plane electronic current variations across semiconducting membranes made of two-dimensional (2D) materials, such as monolayer graphene and molybdenum disulfide. This approach that consists in coupling molecular dynamicsMolecular dynamics (MD) with self-consistent electronic transport modeling is illustrated by examples of applications in the detection of single- (ssDNA) and double-strand (dsDNA), DNA methylationsMethylation (DNA), epigenetic biomarkers, DNA nicks, and DNA with RNA tails, for which statistical signal processing techniques are implemented to improve the signal to noise ratioSignal-to-noise ratio (SNR). Technical issues related to the use of advanced multilayer 2D solid-state nanopores for reducing the conformational noise by electrical tuning and compounded van der Waals interactionsVan der Waals interactions, sensitivity boosting by introducing back gate layer, and the homopolymer distinction via multi-probe nanopore field-effect transistor (FET) are also addressed. Finally, a proof-of-concept analysis for the large-scale parallel biomolecule detection that shows immunity to crosstalk of the in-plane electronic current signals is discussed.

A robust and reliable detection scheme of RNA tails grown on a double-stranded DNA (dsDNA) can pave the way to a denser encoding of DNA-based storage systems that use the punch card mechanism. Here, we develop a systematic algorithmic approach based on signal processing to detect the presence of RNA tails on dsDNA as well as to differentiate the tail lengths from the transverse conductance signal of MoS2 membrane nanopores. Combining all-atom molecular dynamics simulations with electronic transport modeling, we suggest a method to detect RNA tails with lengths of 10, 15, and 20 nucleotides separated by 10 base pairs. Modified dwell times obtained by using normalized DNA velocity provide an easy and intuitive way to distinguish the lengths of the RNA tails. We show that this technique can be extended for multiple tails, separation distances, and substrate DNA lengths.

Nanopore transistors made of vertically stacked monolayer MoS2-hBN in a multi-sensing electronic scheme are predicted to improve sensing robustness and noise reduction in detecting biomolecules such as DNA and proteins. Our approach based on all-atom molecular dynamics simulation coupled with a semi-classical Boltzmann formalism for electronic transport along the layers shows quenching of the conformational motion of the biomolecule translocating through the multi-layer membrane. The synchronization of electronic sensing current signatures across the successive MoS2 probes achieved by time-lagged cross-correlation is seen to enhance the signal-to-noise ratio, notably in the lower frequency spectrum, thereby enabling the identification of homopolymers.

Here, we report on the design tradeoffs between traditional hexagonal and emerging cubic In X Ga (1− X ) N/GaN-based green (520nm≤ λ ≤550nm) light-emitting diodes with special emphasis on the electron blocking layer, number of quantum wells, and thicknesses of quantum wells and barriers. We identified three crucial design rules for cubic green light-emitting diodes: (1) no need for an electron blocking layer; (2) use of a wide quantum well; and (3) choice of thin quantum barriers in multi-quantum well light-emitting diode designs. These design rules increase the internal quantum efficiency of cubic green light-emitting diodes by ∼30.5% under 100A/cm 2 injection with respect to traditional designs. Overall, the design rules of cubic light-emitting diodes and their differentiating nature from the traditional, hexagonal ones are crucial for the advent of next-generation cubic light-emitting diodes.

The onset of electronic current in a doped silicon membrane induced by the long-range Coulomb interaction of ions flowing through a nanofluidic channel is established by a combined computational and analytical approach based on Green's function technique and Boltzmann transport formalism. Characterized by an open circuit voltage and short circuit current, the electronic Coulomb drag provides a new paradigm for power harvesting. In addition, our model predicts a current amplification of the ionic drag current because of the large momentum transfer from heavy ions to charge carriers in silicon, which is achieved for both anions and cations flowing in the nanochannel irrespective of the dopant type in the semiconductor. The analysis indicates the versatility of this effect with respect to the nature of the electrolyte and the semiconducting materials, providing proper tuning of their structures and design configurations.

In conventional hexagonal InGaAlN multiple-quantum-well (MQW) (h-) light-emitting diodes (LEDs), carrier leakage from QWs is the main source of internal quantum efficiency (IQE) degradation without contributing to the LED efficiency droop. Our analysis based on the newly developed Open Boundary Quantum LED Simulator indicates that radiative recombination is hampered by the poor electron–hole wavefunction overlap induced by strong internal polarization for which QW carriers mostly recombine via Auger scattering rather than by radiative processes. By contrast, in non-polar h-LEDs, the IQE peak doubles its value compared to conventional h-LEDs while quenching the efficiency droop by 70% at current density of 100 A/cm2. Those effects are further enhanced in cubic InGaAlN MQW (c-) LEDs for which the IQE peak increases by an additional 30%, and the efficiency droop is further reduced by 80% compared to non-polar h-LEDs, thanks to the larger optical transition matrix element and the strong electron–hole wavefunction overlap in c-LEDs. Overall, a c-LED with a low efficiency droop of 3% at 100 A/cm2 is anticipated, paving a clear pathway toward ultimate solid-state lighting.

Gating in ion transport is at the center of many vital living-substancetransmission processes, and understanding how gating works at an atomic level is essentialbut intricate. However, our understanding andfinite experimentalfindings of subcontinuumion transport in subnanometer nanopores are still limited, which is out of reach of theclassical continuum nanofluidics. Moreover, the influence of ion density on subcontinuumion transport is poorly understood. Here we report the ion density-dependent dynamicconductance switching process in biomimetic graphene nanopores and explain thephenomenon by a reversible ion absorption mechanism. Our molecular dynamics simulationsdemonstrate that the cations near the graphene nanopore can interact with the surfacecharges on the nanopore, thereby realizing the switching of high- and low-conductancestates. This work has deepened the understanding of gating in ion transport

The effect of Auger electron–hole asymmetry on the efficiency droop in indium gallium nitride quantum well (InGaN-QW) light-emitting diodes (LEDs) is investigated through a new open boundary quantum solver based on variational principles: Open Boundary Quantum LED Simulator (OBQ-LEDsim). OBQ-LEDsim eliminates the need for forcing artificial boundary conditions in LED simulations and features explicit expression of wavefunction with high generality, enabling incorporation of wavefunction penetration into barriers, quantum-confined Stark effects, and excitonic effects. As such, the Auger recombination’s primary channel is found to be the hhe Auger recombination because holes are more localized than electrons in the quantum well. Varying the ratio of electron ( $\text{C}_{\mathrm {n}}$ ) to hole ( $\text{C}_{\mathrm {p}}$ ), Auger coefficient $\text{C}_{\mathrm {n}}/\text{C}_{\mathrm {p}}$ , from 0 to $\infty $ suppresses the hhe Auger recombination, resulting in 25% higher electron and hole sheet charge densities in the LED active layer. This increases carrier screening of the polarization-induced electric fields and weakens quantum-confined Stark effects. One observes a 75% increase in the electron and hole square wavefunction overlap and an 8 nm blueshift in the peak emission wavelength. As a result, the efficiency droop in an InGaN-QW LED is reduced by a factor of 2 when the $\text{C}_{\mathrm {n}}/\text{C}_{\mathrm {p}}$ is increased from 0 to $\infty $ , whereas the ambipolar Auger coefficient is overestimated by as much as 62% if the Auger electron–hole asymmetry is neglected ( $\text{C}_{\mathrm {n}}/\text{C}_{\mathrm {p}} \sim ~1$ ).

We show that the coexistence of strong internal polarization and large carrier (i.e., electron and hole) effective mass accounts for ~51% of the efficiency droop under high current densities in traditional (hexagonal-phase) indium–gallium–aluminum–nitride (InGaAlN) light-emitting diodes (h-LEDs) compared to cubic-phase InGaAlN LEDs (c-LEDs). Our analysis based on variational technique on c-LEDs predicts an enhancement of the current density at the onset of the droop, inherently present in green c-LEDs. These effects are a consequence of the polarization-free nature and small carrier effective mass of c-LEDs. Our analysis indicates that, by overlooking the electron–hole wave function overlap, the well-known ABC model is suspected to overestimate the Auger coefficient, leading to questionable conclusions on the efficiency droop. In turn, it shows that the c-LED efficiency droop is much immune to the Auger electron–hole asymmetry, the increase in the Auger coefficient, and, thus, efficiency degradation mechanisms.

On-chip manipulation of charged particles using electrophoresis or electroosmosis is widely used for many applications, including optofluidic sensing, bioanalysis and macromolecular data storage. We hereby demonstrate a technique for the capture, localization, and release of charged particles and DNA molecules in an aqueous solution using tubular structures enabled by a strain-induced self-rolled-up nanomembrane (S-RuM) platform. Cuffed-in 3D electrodes that are embedded in cylindrical S-RuM structures and biased by a constant DC voltage are used to provide a uniform electrical field inside the microtubular devices. Efficient charged-particle manipulation is achieved at a bias voltage of <2–4 V, which is ~3 orders of magnitude lower than the required potential in traditional DC electrophoretic devices. Furthermore, Poisson–Boltzmann multiphysics simulation validates the feasibility and advantage of our microtubular charge manipulation devices over planar and other 3D variations of microfluidic devices. This work lays the foundation for on-chip DNA manipulation for data storage applications.