Surface Acoustic Wave-Induced Electroluminescence Intensity Oscillation in Planar Light-Emitting Devices
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Surface Acoustic Wave-Induced Electroluminescence Intensity Oscillation in Planar LightEmitting Devices Marco Cecchini1, Vincenzo Piazza1, Fabio Beltram1, Martin Ward2, Andrew Shields2, Harvey Beere3 and David Ritchie3 1 Scuola Normale Superiore and NEST-INFM, I-56126 Pisa, Italy. 2 Toshiba Research Europe Limited, Cambridge Research Laboratory, 260 Cambridge Science Park, Milton Road, Cambridge CB4 OWE, United Kingdom. 3 Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, United Kingdom. ABSTRACT Electroluminescence (EL) emission controlled by means of surface acoustic waves (SAWs) in planar light-emitting diodes (pLEDs) is demonstrated. Interdigital transducers (IDTs) for SAW generation were integrated onto pLEDs fabricated following a scheme compatible with SAW propagation [1]. EL in presence of SAW was studied by time-correlated photon-counting techniques. We found intensity oscillation at the SAW frequency (~1 GHz) demonstrating electron injection into the p-type region synchronous with the SAW wavefronts. INTRODUCTION Recently SAWs have attracted the interest of the semiconductor community in view of their interaction properties with two-dimensional-electron-gases (2DEGs) embedded in semiconductor heterostructures [2, 3]. Mechanical waves propagating across the surface of a piezoelectric substrate are associated with potential waves which couple with the free carriers confined in the quantum well. This interaction modifies the 2DEG equilibrium state and the wave speed and amplitude. By measuring the change in amplitude and velocity of the SAW it is possible to extract the frequency and wave-vector dependence of the 2DEG conductivity [2], while the momentum transferred by the SAW to the 2DEG leads to the excitation of dc current or voltage (the so-called acoustoelectric effect) [4, 5, 6]. The discovery of the acoustoelectric effect gave rise to the proposal of innovative devices. Among these Talyanskii et al. proposed the implementation of a novel current standard, demonstrating very precise acoustoelectric current quantization due to charge drag by SAWs through a quantum point contact [7, 8]. Control over the constriction width allowed very precise selection of the number of electrons packed in each SAW minimum down to the single-electrontransport regime. One of the most appealing applications proposed after the first report of the acoustoelectric quantized current was to incorporate single-electron SAW pumps in planar 2D electron/2D hole gas (n-p) junctions to fabricate single-photon sources [9]. In this paper we report on the acoustoelectric effect in pLEDs. Devices containing lateral np junctions and IDTs for SAW generation (SAWLEDs) were fabricated and measured at cryogenic temperatures. We analyzed the optical and transport properties induced by the acoustic perturbation by means of current-voltage (IV), light-voltage (LV) and EL time-resolved measurements. The SAWLED constitutes one of the main building blocks of the SAW-driven single-photon source [9] and, from a more fundamental p
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