Abstract
Potential barriers of different types (rectangular, triangle, parabolic) with a dc-bias and a small ac-signal in the THz-frequency band are investigated in this paper. The height of the potential barrier is modulated by the high frequency signal. If electrons penetrate through the barrier they can emit or absorb usually one or even more energy quanta, thus the electron wave function behind the barrier is a superposition of different harmonics. The time-dependent Schrödinger equation is solved to obtain the reflection and transmission amplitudes and the barrier transmittance corresponding to the harmonics. The electronic current density is calculated according to the Tsu-Esaki formula. If the harmonics of the electron current density are known, the complex admittance and other electrical parameters of the structure can be found.
Highlights
The terahertz frequency band is recently usually considered as the interval 300 GHz–3 THz that corresponds to the submillimeter wavelength range between 1 mm and 100 mm or to photon energy within the range 1.2–12.4 meV
The theory related to the transmittance of different types of potential barriers with dc bias and small high frequency ac signal in the terahertz frequency band was presented in this paper
We have followed the way from the hamiltonian and the time dependent Schrödinger equation to the electric current densities and complex admittance that can be measured in experiments
Summary
The terahertz frequency band is recently usually considered as the interval 300 GHz–3 THz that corresponds to the submillimeter wavelength range between 1 mm and 100 mm or to photon energy within the range 1.2–12.4 meV. Recent rapid progress in nanoelectronics and high frequency technologies necessitates that heterojunctions, superlattices, low-dimensional semiconductor structures, quantum wells and barriers are today standard building blocks of modern electronic devices, which find their application in the field of microwave and submillimeter technology or in photonics. The existence of quantum wells and barriers results in the quantum-based mechanism of electron transport, thermionic emission across the barrier and the tunnelling (thermionic-field-emission) through the barrier These effects should be treated by means of appropriate methods of quantum physics. Nearly the same theoretical approach that is used for investigating of the terahertz frequency band can be applied if the interaction of near-infrared radiation with photonic structures is studied. The aim of this paper is to present results achieved in a theoretical investigation of the high-frequency electron transport across the rectangular, triangular, trapezoidal or parabolic potential barriers that are most frequently used in various nanoelectronic or photonic structures
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