Bistability and discontinuity in the tunnel current of two-dimensional electron-hole layers

Abstract

We present a detailed study of a recently reported discontinuity and bistability in a 12-nm GaAs/AlAs single-barrier p-i-n heterostructure, where a system of spatially separated two-dimensional electron and hole (e-h) layers of equal and tunable density is realized. Both features appear at TՇ300 mK and are strongly enhanced in a magnetic field Bտ10 T perpendicular to the layers, whereas they are suppressed by Bϳ1 T parallel to the layers. They correspond to a discontinuity in the e-h density and in the phase of the current magneto-oscillations. Whereas the high-current state has the expected properties of the uncoupled e-h layers, the low-current state behaves anomalously under all circumstances, and we identify them with a gas of spatially indirect excitons with binding energy 0.03 meVՇE b Շ0.3 meV and 0.5 meVՇE b Շ5 meV at B ϭ0 and Bϭ10 T, respectively. We interpret the bistability as a transition between the two regimes, which arises because of the competition between the in-plane screening, determined by the average e-e (h-h) distance and the magnetic length, and the interlayer e-h attraction.

Undoped electron-hole bilayers in a GaAs∕AlGaAs double quantum well

“…Since then several research groups have studied electron-hole bilayers using doped heterostructures. [2,3,4,5,6,7,8,9,10,11,12] Single layer undoped heterostructures commonly referred to as heterostructure insulated-gate field-effect transistors (HIGFETs) have been investigated previously. [13,14,15] In these studies particular interest was paid to the ultra-low density capability afforded by HIGFETs, and the ability to directly control the density and polarity of the carriers.…”

“…[12] Most of the previous studies were limited by an inability to adjust the densities in the two layers sufficient to match up the density of the 2DEG (n) to the density of the 2DHG (p). This was typically either due to the use of a doped heterostructure [3,4] or a design which lacked a back gate. [5,6,16] The uEHBL architecture allows for independent contacts to each layer, high mobility, and tunable low densities for the 2DEG * Electronic address: jaseamo@sandia.gov and 2DHG.…”

Spatially indirect excitons in coupled quantum wells

“…This can be achieved by using less leaky samples and a pico-second ultrafast laser excitation in resonance with the direct exciton transitions. Secondly, it would be interesting to investigate the possibility of artificially generating cold, dense and long-lived indirect-X systems by tunneling injection mechanisms [237,238]. This would provide new possibilities for exploration of collective quantum phenomena of excitons in solid-state systems.…”

Bound-exciton-induced current bistability in a silicon light-emitting diode

“…However, there have been very few studies on the exciton-induced current bistability in heterostructures. 13 The reason is probably that excitons cannot cause a band bending and redistribution of charge profiles due to their intrinsically neutral-charged states. In this report, we present the observation of an S-type differential resistance in the I -V characteristics of a silicon p -n diode produced by boron ion implantation.…”