Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userSuppressed absolute negative conductance and generation of high-frequency radiation in semiconductor superlattices
67
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
We show that space-charge instabilities (electric field domains) in semiconductor superlattices are the attribute of absolute negative conductance induced by small constant and large alternating electric fields. We propose the efficient method for suppression of this destructive phenomenon in order to obtain a generation at microwave and THz frequencies in devices operating at room temperature. We theoretically proved that an unbiased superlattice with a moderate doping subjected to a microwave pump field provides a strong gain at third, fifth, seventh, etc. harmonics of the pump frequency in the conditions of suppressed domains.
rate research
Read More
We theoretically investigated the scheme allowing to avoid destructive space-charge instabilities and to obtain a strong gain at microwave and THz frequencies in semiconductor superlattice devices. Superlattice is subjected to a microwave field and a generation is achieved at some odd harmonics of the pump frequency. Gain arises because of parametric amplification seeded by harmonic generation. Negative differential conductance (NDC) is not a necessary condition for the generation. For the mode of operation with NDC, a limited space-charge accumulation does not sufficiently reduce the gain.
We examine the high-frequency differential conductivity response properties of semiconductor superlattices having various miniband dispersion laws. Our analysis shows that the anharmonicity of Bloch oscillations (beyond tight-binding approximation) leads to the occurrence of negative high-frequency differential conductivity at frequency multiples of the Bloch frequency. This effect can arise even in regions of positive static differential conductivity. The influence of strong electron scattering by optic phonons is analyzed. We propose an optimal superlattice miniband dispersion law to achieve high-frequency field amplification.
The linear conductance spectrum of a metallic graphene junction formed by interconnecting two gapless graphene nanoribbons is calculated. A strong conductance suppression appears in the vicinity of the Dirac point. We found that such a conductance suppression arises from the antiresonance effect associated with the edge state localized at the zigzag-edged shoulder of the junction. The conductance valley due to the antiresonance is rather robust in the presence of the impurity and vacancy scattering. And the center of the conductance valley can be readily tuned by an electric field exerted on the wider nanoribbon.
A fractal-like alignment of quantum wells is shown to accommodate resonant states with long lifetimes. For the parameters of the semiconductor heterostructure GaAs/Al$_{0.4}$Ga$_{0.6}$As with the well depth 300meV, a resonant state of the energy as high as 44meV with the lifetime as long as 2.8{mu}s is shown to be achievable.
Weakly coupled semiconductor superlattices under dc voltage bias are excitable systems with many degrees of freedom that may exhibit spontaneous chaos at room temperature and act as fast physical random number generator devices. Superlattices with identical periods exhibit current self-oscillations due to the dynamics of charge dipole waves but chaotic oscillations exist on narrow voltage intervals. They disappear easily due to variation in structural growth parameters. Based on numerical simulations, we predict that inserting two identical sufficiently separated wider wells increases superlattice excitability by allowing wave nucleation at the modified wells and more complex dynamics. This system exhibits hyperchaos and varieties of intermittent chaos in extended dc voltage ranges. Unlike in ideal superlattices, our chaotic attractors are robust and resilient against noises and against controlled random disorder due to growth fluctuations.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
