transistor placed on the transport path. The EXAT electrode configuration (cf. Fig. \[EXAT\](a)) is similar to the exciton optoelectronic transistor introduced in Refs.[@Ref15; @Ref16; @Ref17]. Here, the voltage applied to the gate electrode (G) creates (via the QCSE) a tunable energy barrier, which controls the acoustically driven IX flow between the source (S) and the drain (D) electrodes. In contrast to its optoelectronic counterpart, the IX flow through the EXAT is acoustically (rather than diffusion or drift-) driven with the flow direction defined by the SAW propagation direction. Note that, in an EXAT, the roles of the source and drain electrodes are interchangeable simply by reverting the SAW propagation direction (not shown). To simplify the notation, we denote by $"source"$ the port with the smaller area.

![(a) Top view of the EXAT showing the source (S), drain (D) and gate (G) electrodes. The G electrode is 1.5 $\mu$m wide and separated by the same distance from the adjacent S and D regions. The lower color plots display PL images of the acoustic transport of IXs across the EXAT recorded in the (b) ON state (with biases V$_{S}$=V$_{D}$=V$_{G}$=-1.4 V, cf. right inset) and (c) OFF state (V$_{S}$=V$_{D}$=-1.4 V, V$_{G}$=2.5 V, cf. 