Negative differential conductivity in semiconductor superlattices using parabolic and sinusoidal miniband dispersion equations

Radiative detectors and devices operating in the range (0.2-10) terahertz and room temperature are needed. The need is created by fast advances of the science and terahertz technologies in the domain of astronomy to biosecurity. By the advances of molecular beam epitaxy (MBE) the growth of semiconductor superlattices of the order of 100 A° is performed. This lattice constant is big and could reveal high field non-ohmic behaviors. The negative differential conductivity (NDC) arises from the grate numbers of electrons in the proximity edge of miniband boundary. The velocity of electrons approaching to the miniband is reduced, causing the NDC effect. In this article the NDC in semiconductor superlattices for sinusoidal and periodic square -well potentials was studied. The extracted maximum carrier drift velocities for a superlattice semiconductor were nearly 1.8x105 m/s and 2.6x105 m/s respectively and the obtained ratio of maximum drift velocity to the corresponding minimum was more than 3 for the two potentials. Also the NDC in semiconductor superlattices for parabolic and sinusoidal dispersion equations at different frequencies was investigated. In the parabolic dispersion equation, near the harmonic Bloch oscillations at frequencies between even and odd harmonic oscillations, the high frequency NDC was observed.