Transport properties of a shunted surface superlattice in an external magnetic field

We study the transport through a shunted surface superlattice system in the presence of an external magnetic field. Such a system consists of a weakly doped, instability free superlattice (shunt) that is overgrown on the edge with a two-dimensional electron system (surface superlattice). A magnetic field parallel to a static applied electric field along the superlattice axis induces current resonances in the shunt characteristics which are explained by Stark-cyclotron resonances. These resonances support the conclusion that the field alignment in the shunted surface superlattice structure is homogeneous. An increasing magnetic field perpendicular to the transport direction leads to characteristic crossings of the current-voltage characteristics of both shunt and surface superlattice. They are explained by a semiclassical model which assumes a competition between the magnetic and electric localization of the miniband electrons. We conclude that our structure indeed presents a domain free high density superlattice and might therefore be a promising candidate for the realization of an active electrically driven Bloch oscillator.

Figure 1

(a) Schematic drawing of possible transport channels resulting in SCRs. (b) Numerical results for miniband transport in a superlattice in the presence of a perpendicular magnetic field.

Figure 2

(a) Schematic drawing of the sample structure. (b) Relaxation times and transport regimes. (c) Transport contributions in the sample structure. The inset shows the SSL band structure for two different densities.

Figure 3

(a) Current-voltage traces of the shunt for several magnetic field values applied parallel to the current. (b) Positions of magnetic field-induced features of the traces in (a).

Figure 4

(a) Current-voltage characteristics of the described SSL at a density of $1.7\times {10}^{11}{\mathrm{cm}}^{-2}$ for magnetic fields from 1 to $13\mathrm{T}$ (lines). Also the $B=0$ trace is shown (symbols). (b) Position and height of the NDC peak of the data in panel (a).

Figure 5

In the figure the resistance $R=V∕I$ for a SD voltage of $5\mathrm{mV}$ is plotted vs the square of the magnetic field $B$. The gray line indicates a linear fit in the region of large $B$. The inset shows a magnification of the current-voltage data of Fig. 4a at low bias, indicating the crossover from positive to negative MR in the limit $B\to 0$.

Figure 6

(a) Numerical results for miniband transport in a superlattice in the presence of a perpendicular magnetic field assuming transport parameters extracted from the experiment. (b) Position and height of the NDC peak in panel (a).

Figure 7

Gain of an experimentally realized SSL assuming two different effective electron temperatures.