Transverse magnetotransport anisotropy in a semiconductor superlattice

Abstract

The vertical magnetotransport properties of GaAs–AlAs superlattices have been investigated as a function of the in-plane magnetic field orientation. Two main effects were observed: (i) the influence of the roughness anisotropy with respect to the crystallographic orientation, and (ii) the nonparabolicity of the energy in the plane of the layers. The interface fluctuations induced a modulation of the miniband transport with a period of 180°. The nonparabolic energy of the deflected electronic orbits also induced a modulation of the vertical transport but with a period of 90°. Both observed effects are in qualitative agreement with a semiclassical description of the Boltzmann transport equation.

Absolute Negative Conductivity and Spontaneous Current Generation in Semiconductor Superlattices with Hot Electrons

“…A magnetic field increases the value of the electric field at which the current reaches its maximum value ( Fig. 1b), as has been observed in recent experiments [2]. Finally, for larger magnetic fields ( Fig.…”

“…In clean SSLs with only modest fields, electrons can reach the negative effective mass (NEM) portion of the miniband before scattering. For an electric field oriented along the SSL growth axis, the current-voltage characteristic exhibits a peak followed by negative differential conductivity (NDC) when a significant fraction of electrons explore the NEM region of the miniband [1]; with an additional magnetic field perpendicular to the growth axis, NDC occurs at a larger bias because the magnetic field impedes the increase of crystal momentum along the growth axis [2].…”

“…1c), the current-voltage characteristic from the balance equations has a region of multistability with three possible currents. For SSL parameters of ∆ = 23 meV, a = 84 Å, and γ vy = γ vz = γ ε = 1.5 × 10 13 sec −1 , [2], multistability requires a magnetic field of 21 T, but the semiclassical balance equation is not applicable at such large fields. However, for SSL parameters of ∆ = 22meV, a = 90 Å, and γ vy = γ vz = γ ε = 10 12 sec −1 , [7], multistability should occur for a modest magnetic field of 1.4 T.…”

Multistability, absolute negative conductivity and spontaneous current generation in semiconductor superlattices in large magnetic fields

“…The current-voltage characteristic of an SSL exhibits a peak followed by NDC; and a magnetic field in the plane of the QWs increases the critical electric field at which the peak current is attained [5,6]. As is evident in Fig.…”

“…With the time-independent electric field ω B and magnetic field B, the SSL current I = −eN A( a/2 )v z,ss , where N is the carrier concentration, A is the cross-sectional area, and v z,ss is the steady-state solution to eqn (5). Considering the steady-state solutions to eqns (4)- (6), we obtain a cubic equation relating v z,ss to the applied voltage, with C = B 2 /γ vy…”