Electrically modulated light-emitting diodes driven by resonant and antiresonant tunneling between Cr${}_2$Ge${}_2$Te${}_6$ electrodes

Abstract

Exploring the electron tunneling mechanisms in diverse materials systems constitutes a versatile strategy for tailoring the properties of optoelectronic devices. In this domain, bipolar vertical tunneling junctions composed of van der Waals materials with vastly different electronic band structures enable simultaneous injection of electrons and holes into an optically active material, providing a universal blueprint for light-emitting diodes (LEDs). Efficient modulation of the injection efficiency has previously been demonstrated by creating resonant states within the energy barrier formed by the luminescent material. Here, we present an alternative approach towards resonant tunneling conditions by fabricating tunneling junctions composed entirely from gapped materials: Cr${}_2$Ge${}_2$Te${}_6$ as electrodes, hBN as a tunneling barrier, and monolayer WSe${}_2$ as a luminescent medium. The characterization of such LEDs revealed a nonmonotonous evolution of the electroluminescence intensity with the tunneling bias. The dominant role driving the characteristics of the electron tunneling was associated with the relative alignment of the density of states in Cr${}_2$Ge${}_2$Te${}_6$ electrodes. The unique device architecture introduced here presents a universal pathway towards LEDs operating at room temperature with electrically modulated emission intensity.

8 pages, 4 figures + SI

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