Hybrid Metal–Semiconductor Nanostructure for Ultrahigh Optical Absorption and Low Electrical Resistance at Optoelectronic Interfaces

Abstract

Engineered optoelectronic surfaces must control both the flow of light and the flow of electrons at an interface; however, nanostructures for photon and electron management have typically been studied and optimized separately. In this work, we unify these concepts in a new hybrid metal-semiconductor surface that offers both strong light absorption and high electrical conductivity. We use metal-assisted chemical etching to nanostructure the surface of a silicon wafer, creating an array of silicon nanopillars protruding through holes in a gold film. When coated with a silicon nitride anti-reflection layer, we observe broad-band absorption of up to 97% in this structure, which is remarkable considering that metal covers 60% of the top surface. We use optical simulations to show that Mie-like resonances in the nanopillars funnel light around the metal layer and into the substrate, rendering the metal nearly transparent to the incoming light. Our results show that, across a wide parameter space, hybrid metal-semiconductor surfaces with absorption above 90% and sheet resistance below 20 Ω/□ are realizable, suggesting a new paradigm wherein transparent electrodes and photon management textures are designed and fabricated together to create high-performance optoelectronic interfaces.

Effectively Transparent Front Contacts for Optoelectronic Devices

“…As a result, many groups have recently proposed design schemes to mitigate front contact losses, such as less absorbing transparent conductive oxides, [4][5][6][7][8] or less refl ective metal contacts such as nanowire grids, [ 9,10 ] fractal contacts, [ 11 ] contacts with different shapes, [12][13][14][15][16] and various other approaches. [17][18][19][20][21] Very high contact transparency usually comes at the expense of reduced conductivity, which in turn leads to series resistance and device electrical losses. A comparison of the photonic designs for different recently developed contacts is shown in Section S3 (Supporting Information).…”

Optical Design of Textured Thin-Film CIGS Solar Cells with Nearly-Invisible Nanowire Assisted Front Contacts

“…This shows that with a texture height/period aspect ratio of about 1, the total reflection is significantly lower than the surface coverage of the metal. Apparently, the light is coupled into the structure and circumvents the metal film, as mentioned in [27]. At a height of 2200 nm, the reflection has almost vanished and virtually all the light is absorbed, i.e., a device with this texture would be black, in spite of the “bare” flat silver surface and also the absorption of the silver, which is depicted in purple and is hardly visible in Figure 2d.…”

“…They have studied only flat layers, while our case shows that these trends become more pronounced for the textured layer. This leads us to believe that for a textured layer with a metallic grid, the peaks as shown in the figures are the result of various optical phenomena, including surface plasmon resonances, but Mie-like resonance might also play a role, as described by Narasimhan et al, which would be responsible for confining light to the structure [27]. …”

“…This was followed by a gold catalyzed etching step, whereby the gold ends up at the bottom of the etched crevice [27]. Such a texturization procedure resulted in a decrease of the initial reflection from 50% for a flat sample (before etching) down to 19% for gold in 330 nm deep trenches after etching.…”

Quadratic Electro-Optic Effect and Electro Absorption Process of Multi-layer Spherical Quantum Dot Enhanced by Metal Nanoparticle

“…In recent years, the interaction of quantum dots and metal nanoparticles (MNP) have been one of the most important subjects studied in hybrid structure [23][24][25][26][27][28] because the MNP strengthens the local field felt by the QD, which may enhance emission and luminescence [29]. Hybrid QD-MNP systems have been used for ultrahigh optical absorption and low electrical resistance at optoelectronic interfaces [30] and detect the possible signature of Majorana fermions [31], coherent controllable transport of a plasmonic waveguide [32], colorimetric measurements of DNA conjugations [33,34], laser systems without cavities [35][36][37], manipulation of heat generation in MPs [38,39], energy transfer processes in superstructures formed via bio-molecules [40], etc. Plasmonic field enhancement via MNPs has also been used for various device applications such as optical and plasmonic antennas [41][42][43][44], quantum nanosensor [45], nonlinear switching [46], and light emitting devices [47].…”