Electrical-Driven Plasmon Source of Silicon Based on Quantum Tunneling

Abstract

An efficient silicon-based light source presents an unreached goal in the field of photonics, due to Silicon's indirect electronic band structure preventing direct carrier recombination and subsequent photon emission. Here we utilize inelastically tunneling electrons to demonstrate an electrically-driven light emitting silicon-based tunnel junction operating at room temperature. We show that such a junction is a source for plasmons driven by the electrical tunnel current. We find that the emission spectrum is not given by the quantum condition where the emission frequency would be proportional to the applied voltage, but the spectrum is determined by the spectral overlap between the energy-dependent tunnel current and the modal dispersion of the plasmon. Experimentally we find the highest light outcoupling efficiency corresponding to the skin-depth of the metallic contact of this metalinsulator-semiconductor junction. Distinct from LEDs, the temporal response of this tunnel source is not governed by nanosecond carrier lifetimes known to semiconductors, but rather by the tunnel event itself and Heisenberg's uncertainty principle.

Silicon-Based Quantum Mechanical Tunnel Junction for Plasmon Excitation from Low-Energy Electron Tunneling

“…Ref 24 suggests that the visible light emission is due to luminescent centers caused by defects and impurities (mainly oxygen vacancies) in the SiO 2 film in their devices. In ref 33, Goktas and colleagues propose that SPP excitation and scattering is the dominant light emission mechanism, but for the following three reasons, we disagree with their interpretation: (i) the light emission in their system lacks the spectral peak shift as a function of V, (ii) their given I(V) curves show very clear rectification, and (iii) their light emission intensity is far away from the quantum cutoff regime. These observations indicate that their junctions are dominated by thermionic emission and associated electroluminescence.…”

“…Similarly, Wang et al 41 also applied a very large DC voltage bias (5∼7 V) to Si−SiO 2 −Au MISJs with N d = 2.5 × 10 19 cm −3 and observed light emission attributed to decaying SPPs, however, they used a barrier thickness of 10 nm, which is too thick for tunneling to occur and, therefore, the light emission likely involved dielectric breakdown. Goktas et al 33 observed light emission from MISJs with p-type silicon doped with N d = 2 × 10 17 cm −3 and proposed that tunneling of accumulated holes generated an MISJ cavity mode that outcoupled to interface SPPs, scattering to photons. This mechanism is unlikely given the low doping levels and lack of spectral blueshift characteristic of SPP excitation in tunneling junctions.…”

Highly-efficient electrically-driven localized surface plasmon source enabled by resonant inelastic electron tunneling

“…It is a signature of IET-based sources 49 , and can be described by the quantum relation , where is the electron charge. The SP radiation power spectrum can be expressed as 26 , 30 , 31 where is the spectral inelastic transition rate in vacuum, is the vacuum LDOS, is the device LDOS, and is the SP radiation efficiency. The spontaneous emission model developed for IET-based sources was used to calculate (Supplementary Note 2 ), FEM simulations were applied to obtain the LDOS enhancement (Supplementary Note 3 ), while is determined by the ratio of the SP excitation power to the total power dissipation as where the total dissipated power consists of not only the SP excitation part , but also the absorption loss by the device materials and the far-field radiative part (Supplementary Note 3 ).…”

“…Recently, direct electrical excitation of SPs via inelastic electron tunneling (IET) in metal-insulator-metal (MIM) junctions has reemerged as a promising ultrafast source to drive the integrated plasmonic circuitries 14 , 15 , 24 , 25 . Since this quantum-mechanical tunnel event is governed by Heisenberg’s uncertainty principle, IET-based plasmonic sources could have a temporal response as fast as few fs at the visible/near-infrared (NIR) frequencies 26 – 29 , limited only by the RC time constant of the sources. Thus, an IET-enabled electrically-driven SP source provides the most appealing strategy for addressing the requirement in bandwidth promised by plasmonic circuitries.…”

Excitation of Surface Plasmons by Inelastic Electron Tunneling

“…It is worth mentioning that in addition to plasmon excitation based on metallic tunnel junctions plasmon and light emission can also be generated with metal-insulator-semiconductor (MIS) tunnel junctions [60]. The advantage of the MIS tunnel junctions is that they can be directly integrated into, e.g., a silicon photonic waveguides for on-chip applications [61,62].…”