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

2001; American Physical Society; Volume: 63; Issue: 11 Linguagem: Inglês

10.1103/physrevb.63.115307

1095-3795

A. Parlangeli, Peter C. M. Christianen, J. C. Maan, M. Henini,

Semiconductor Quantum Structures and Devices

We present a detailed study of a recently reported discontinuity and bistability in a 12-nm GaAs/AlAs single-barrier $p\ensuremath{-}i\ensuremath{-}n$ heterostructure, where a system of spatially separated two-dimensional electron and hole $(e\ensuremath{-}h)$ layers of equal and tunable density is realized. Both features appear at $T\ensuremath{\lesssim}300 \mathrm{mK}$ and are strongly enhanced in a magnetic field $B\ensuremath{\gtrsim}10 \mathrm{T}$ perpendicular to the layers, whereas they are suppressed by $B\ensuremath{\sim}1 \mathrm{T}$ parallel to the layers. They correspond to a discontinuity in the $e\ensuremath{-}h$ density and in the phase of the current magneto-oscillations. Whereas the high-current state has the expected properties of the uncoupled $e\ensuremath{-}h$ layers, the low-current state behaves anomalously under all circumstances, and we identify them with a gas of spatially indirect excitons with binding energy $0.03 \mathrm{meV}\ensuremath{\lesssim}{E}_{b}\ensuremath{\lesssim}0.3 \mathrm{meV}$ and $0.5 \mathrm{meV}\ensuremath{\lesssim}{E}_{b}\ensuremath{\lesssim}5 \mathrm{meV}$ at $B=0$ and $B=10 \mathrm{T},$ 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 $e\ensuremath{-}e (h\ensuremath{-}h)$ distance and the magnetic length, and the interlayer $e\ensuremath{-}h$ attraction.