Indirect excitons in a potential energy landscape created by a perforated electrode

Abstract

We report on the principle and realization of an excitonic device: a ramp that directs the transport of indirect excitons down a potential energy gradient created by a perforated electrode at a constant voltage. The device provides an experimental proof of principle for controlling exciton transport with electrode density gradients. We observed that the exciton transport distance along the ramp increases with increasing exciton density. This effect is explained in terms of disorder screening by repulsive exciton-exciton interactions. V C 2016 AIP Publishing LLC. 1-12 Due to the spatial separation, the IXs also acquire a built-in dipole moment ed, where d is the approximate distance between the QW centers. The dipole moment can be explored to control the IX energy: an electric field F z applied perpendicular to the QW plane shifts the IX energy by E ¼ ÀedF z .13 These properties are advantageous for creating excitonic devices and studying the transport of IXs in electrostatic in-plane potential landscapes Eðx; yÞ ¼ ÀedF z ðx; yÞ.IX transport has been studied in various potential landscapes that were created by laterally modulated voltage V(x, y). These potential landscapes include ramps, 1,6,14 An alternative method for creating potential landscapes for IXs was proposed in Ref. 34, which is based on the lateral modulation of the electrode density rather than voltage. Divergence of the electric field around the periphery of an electrode reduces the normal component F z . This enables one to control F z , and thereby the potential energy landscape for IXs, by adjusting only the electrode density while keeping the entire device at a constant, uniform voltage. This method is beneficial compared to the voltage modulation method because it does not require an energy dissipating voltage gradient. One instance of this method based on varying the electrode width-the shaped electrode methodhas been used to create confining potentials for IXs in traps 18 and ramps. 14,24 In this work, we present an excitonic device based on the electrode density modulation in which a potential energy gradient is created by a perforated electrode at a constant

Split-gate device for indirect excitons

“…These properties include: (i) IXs have built-in dipole moments ed, allowing the control of IX energy by voltage, where the IX energy shifts as δE = −edF z (d is the separation between the electron and hole layers, F z is voltage controllable electric field in the structure growth direction). Various in-plane potential landscapes formed by voltage for IXs were studied in earlier works, including excitonic ramps [12][13][14], static [15][16][17][18][19] and moving [20] lattices, traps [21][22][23][24][25][26], and transistors [27]. (ii) Long IX lifetimes allow them to travel long distances in mesoscopic devices before recombination [12-14, 18-20, 27].…”