Electroluminescence Enhancement via Grating on a Si-based Plasmonic Metal-Insulator-Semiconductor Tunnel Junction
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Electroluminescence Enhancement via Grating on a Si-based Plasmonic Metal-InsulatorSemiconductor Tunnel Junction Hasan Goktas, and Volker J. Sorger Electrical and Computer Engineering, The George Washington University, 2121 I St. NW, Washington, DC 20052 ABSTRACT Here we fabricated and characterized a CMOS compatible metal-insulator-semiconductor (MIS) plasmonic tunnel junction for Si-based photonic circuitry. A grating structure was realized on MIS plasmonic tunnel junction via focused-ion-beam milling (FIB) to increase the intensity of the light emission that occurs during inelastic electron tunneling. Approximately 65 times higher intensity of light emission is achieved with the grating structure during the measurements. INTRODUCTION Conventional microprocessor interconnect performance cannot keep pace with semiconductor device scaling. To continue the pace of processor development which is critical towards this data-driven demand, interconnect technology must move beyond the inefficient charging and discharging of metal wires. The case for implementing optical interconnects has been made and the benefits are manifest [1]. The large bandwidth of optical waveguides can accommodate densely multiplexed signals. While an electrical line is limited to signaling at the clock frequency, an optical line can support channel capacities beyond terabits per second [2]. Optical signals provide speed-of-light signaling, mitigation of skew and voltage isolation problems, and near-ideal impedance matching at the photo-detector [1]. In addition to large performance gains, silicon photonics is a mature industry with detectors, modulators, waveguides and filters routinely fabricated with CMOS processing. The missing element in the realization of optical Si-based photonic circuitry is the silicon light source [3]. Development of that critical device with optimum performance, especially the intensity of light emission is the subject of this work. Different methods applied in previous works [4-5] to increase the light emission in MIS structures; however, the maximum increase in the light emission of these previous works is no greater than two times. Here we propose grating structure as a means of increasing the intensity of light emission approximately 65 times. THEORY The schematic and mechanism of the proposed device to investigate is shown in figure 1. Note, the eigenmode of this structure is a photonic-plasmonic hybrid mode, which allows for high deep sub-diffraction limited optical modes [2], [6-8]. Electrically, the band diagram of this MIS junction is schematically shown in figure 1(b). The underlying physical processes are elastic and inelastic electron tunneling controlled by bias voltage. With each scattering event at the barrier, there exists a finite probability that the electron will tunnel into the conduction band to the semiconductor counter-electrode, conserving electron kinetic energy. After tunneling, the hot electron achieves thermal equilibrium, giving up its energy as heat. In contrast, inelastic electron
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