Room-temperature electrical control of exciton flux in a van der Waals heterostructure

Abstract

Devices that rely on the manipulation of excitons-bound pairs of electrons and holes-hold great promise for realizing efficient interconnects between optical data transmission and electrical processing systems. Although exciton-based transistor actions have been demonstrated successfully in bulk semiconductor-based coupled quantum wells, the low temperature required for their operation limits their practical application. The recent emergence of two-dimensional semiconductors with large exciton binding energies may lead to excitonic devices and circuits that operate at room temperature. Whereas individual two-dimensional materials have short exciton diffusion lengths, the spatial separation of electrons and holes in different layers in heterostructures could help to overcome this limitation and enable room-temperature operation of mesoscale devices. Here we report excitonic devices made of MoS-WSe van der Waals heterostructures encapsulated in hexagonal boron nitride that demonstrate electrically controlled transistor actions at room temperature. The long-lived nature of the interlayer excitons in our device results in them diffusing over a distance of five micrometres. Within our device, we further demonstrate the ability to manipulate exciton dynamics by creating electrically reconfigurable confining and repulsive potentials for the exciton flux. Our results make a strong case for integrating two-dimensional materials in future excitonic devices to enable operation at room temperature.

Control of the orbital character of indirect excitons in MoS2/WS2 heterobilayers

“…The reduced overlap of the electron-hole wavefunctions entails greatly prolonged exciton lifetimes of more than 100 ns [10,12], exceeding the lifetime of intralayer excitons by several orders of magnitude [13,14]. The long lifetimes enable the formation of thermalized dense exciton ensembles [15], which, together with IX diffusion over several micrometers [16,17], sets up the possibility to operate excitonic devices [16,18].…”

Metal–Organic Frameworks in Modern Physics: Highlights and Perspectives

“…[46] It has been shown that energy transfer by excitons can be described by a Dexter triplet-to-triplet (exchange) mechanism with multistep incoherent exciton hopping, or a Förster mechanism involving one-step jumping over longer distances. [42] An ability to generate excitons by light, and electrical control of these excitons, also supports MOF application in optoelectronics in the near future, [56] and we believe that MOFs can compete with materials such as inorganic 2D vdW crystals and heterostructures, [57] organic polymers, and crystals for micro-and nano-electronic devices that operate based on the Bose-Einstein condensation effect. [55] Intriguingly, the structure of MOFs also affects the exciton migration path, as it was discovered that mixed Ru/Os structures constituted 1D or 3D hopping networks.…”

Gate-tunable trion switch for excitonic device applications

“…The monolayer semiconducting transition metal dichalcogenides (MoS 2 , WS 2 , MoSe 2 , and WSe 2 ) exhibit strongly bound two-dimensional excitons with a binding energy on the order of few hundreds of meV, making these ultra-thin monolayers an excellent test bed for excitonic manipulation even at room temperature [1][2][3][4][5]. The neutral excitons (X 0 ) show excellent valley polarization and valley coherence properties that can be readily probed through initialization by circularly and linearly polarized photons, respectively, followed by detection through a circular or linear analyzer [6][7][8][9][10][11].…”

“…Recently, this problem has been addressed by creating inter-layer exciton [20][21][22][23][24] to suppress the fast radiative decay, and exciton transport over several micrometer in the plane of the layered material has been demonstrated [4]. An external gate control has also been achieved by modulating the binding energy of the neutral exciton [4,5].…”

“…In addition, transport of the exciton also remains challenging due to the ultra-fast radiative recombination of exciton [12][13][14][15][16] resulting from the high oscillator strength [17][18][19] -limiting the application of excitonic devices.Recently, this problem has been addressed by creating inter-layer exciton [20][21][22][23][24] to suppress the fast radiative decay, and exciton transport over several micrometer in the plane of the layered material has been demonstrated [4]. An external gate control has also been achieved by modulating the binding energy of the neutral exciton [4,5].In this regard, the charged exciton or trion (X − ) is promising since its intensity can be readily controlled electrically by modulating the doping density using a gate voltage. In addition, the trion, while being optically initiated, can be electrically detected in a spatially nonlocal manner through measuring a charge current [25].…”