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Formation of 45° Silicon (110) Surface Using Triton X- <i>n</i> Surfactants in Potassium Hydroxide for Infrared Applications
摘要： Silicon (Si) micromirrors are an integral feature for many micro-optomechanical systems (MOEMS). Such mirrors are generally wet etched in alkaline solution at elevated temperature. For 90? beam steering applications, 45? slanted Si (110) plane is the prime choice fabricated with the incorporation of tensioactive surfactants. Here, Triton-Si and Triton-hydroxide (OH?)/H2O interaction using varying hydrophilic chain length Triton (X-45, X-100 and X-405) were investigated. The surfactant concentration was varied from 0 to 1000 ppm in potassium hydroxide (KOH). Triton molecules were shown to adsorb preferentially on (110) than on (100) surface. Longer chain length Triton hampered OH? access to Si surface resulting in slower etch rate. In contrast, contact angle measurement suggested that shorter Triton interfaced better with Si surface. Later, Si wafers etched in Triton 10 ppm – KOH were examined. The measured output for (110)X-45, (110)X-100, (110)X-405 and polished Si wafer reference (Rq < 5?) mirrors were 0.58, 0.76, 0.72 and 1.25 mW, respectively. Subsequently, Si-SiO2 thin film in [HLHL]2-substrate configuration was fabricated. Broadband micromirror for use in 3.0–5.5 μm spectrum range was experimentally realized with reflected efficiency of 73%.
关键词： wet etching,optical measurement,Silicon micromirrors,Triton X-n,surface roughness,potassium hydroxide,surfactants
更新于2025-09-23 15:23:52
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The morphology evolution of selective area wet etched commercial patterned sapphire substrates
摘要： Patterned sapphire substrates (PSS) have been widely used to enhance the light output power of light emitting diodes (LEDs). The morphology and shape of the PSS have a great influence on the performance of the LEDs. In this work, commercial PSS is reprocessed utilizing selective-area wet etching approach, in which selective-area SiO2 mask is fabricated through partial exposure lithography instead of conventional overlay lithography. By precisely controlling the exposure time, the etching process can be controlled to take place only on the top of the PSS. Various surface morphology including pyramid, volcano, clover and closed-packaged inverted pyramid can be attained from the evolution of the selective-area etched PSS. The mechanism of the selective-area etched sapphire is correlated to the slant angle of the pattern surface and the SiO2 mask pattern.
关键词： Wet etching,Selective-area,Patterned sapphire substracte
更新于2025-09-23 15:22:29
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[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Wet-Chemically Textured Ultra-Thin GaAs Solar Cells with Dielectric/Metal Rear Mirrors
摘要： The rear-side contact layer of ultra-thin GaAs solar cells was textured using a simple, one-step wet chemical approach. A ZnS/Ag double layer was conformally deposited to function as a diffusive rear mirror. Local Ohmic contact points provided electrical contact directly to the Ag. The textured solar cells were compared with planar reference cells fabricated on the same wafer and a clear enhancement of long-wavelength quantum efficiency and short-circuit current was observed in the textured cells. Both architectures showed FF > 80% and VOC > 1 V. Additionally, the rear-side texture increases the external luminescent efficiency by enhancing outcoupling of luminescence.
关键词： light trapping,ultra-thin GaAs solar cells,dielectric mirror,wet etching
更新于2025-09-23 15:19:57
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[IEEE 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Huangshan, China (2019.8.5-2019.8.8)] 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Economical Solution for Cladding Etched Optical Fibers
摘要： We demonstrate an economical wet etching solution for optical fibers using glass etching cream. The etching performance and surface quality on optical fibers are investigated. The solution offers good controllability and repeatable outcomes.
关键词： optical fibers,glass etching cream,Chemical wet etching
更新于2025-09-16 10:30:52
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A facile light‐trapping approach for ultrathin GaAs solar cells using wet chemical etching
摘要： Thinning down the absorber layer of GaAs solar cells can reduce their cost and improve their radiation hardness, which is important for space applications. However, the lighttrapping schemes necessary to achieve high absorptance in these cells can be experimentally challenging or introduce various parasitic losses. In this work, a facile lighttrapping approach based on wet chemical etching is demonstrated. The rear‐side contact layer of ultrathin GaAs solar cells is wet‐chemically textured in between local Ohmic contact points using an NaOH‐based etchant. The resulting contact layer morphology is characterized using atomic force microscopy and scanning electron miscroscopy. High broadband diffuse reflectance and haze factors are measured on bare and Ag‐coated textured contact layers. The textured contact layer is successfully integrated as a diffusive rear mirror in thin‐film solar cells comprising a 300‐nm GaAs absorber and Ag rear contact. Consistent increases in short‐circuit current density (JSC) of approximately 3 mA cm?2 (15%) are achieved in the textured cells, while the open‐circuit voltages and fill factors do not suffer from the textured rear mirror. The best cell achieves a JSC of 24.8 mA cm?2 and a power conversion efficiency of 21.4%. The textured rear mirror enhances outcoupling of luminescence at open circuit, leading to a strong increase in the external luminescent efficiency.
关键词： ultra‐thin GaAs,wet etching,textured III‐V solar cells,light trapping,luminescence outcoupling
更新于2025-09-12 10:27:22
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Surface improvement investigation of sol–gel SiO <sub/>2</sub> cladding for waveguide device passivation
摘要： The sol–gel method is a well-known process for SiO2 formation on top of a semiconductor-based waveguide. This method does not require expensive equipment or SiH4 gas. However, it may result in difficulty with wet-etching, which prevents proper current injection into the semiconductor layer. We have investigated the surface condition of sol–gel SiO2 on top of Si, and have confirmed that the main causes of the anti-etching property might be due to the formation of a polymer layer after the curing process. To improve the surface condition, plasma ashing, in addition to 700 °C curing, is proposed. Regular wet etching of SiO2 layer on Si with a ratio of 1800 nm min?1 has been successfully confirmed.
关键词： SiO2,waveguide passivation,plasma ashing,sol–gel method,polymer layer,wet etching
更新于2025-09-11 14:15:04
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Impact of micro-texturization on hybrid micro/nano-textured surface for enhanced broadband light absorption in crystalline silicon for application in photovoltaics
摘要： This paper reports investigation on hybrid micro/nanotextures for enhanced broadband absorption in crystalline silicon(c-Si) for application in photovoltaics. Microscale pyramids are fabricated using sodium hydroxide (NaOH) solution, etched at different durations. Nanowires on pyramids are formed using metal-assisted chemical etching (MACE). With 30 min of NaOH etching, pyramids with 3–5 μm heights (3–7 μm widths) are formed. The pyramids reduce broadband reflection of the c-Si through enhanced scattering. After MACE, nanowires with 450–600 nm heights (30–40 nm widths) are obtained. With the nanowires, weighted average reflection (WAR) for all samples reduces significantly, owing to enhanced light coupling by the nanowires and increased light scattering by the pyramids. The sample with 30 min NaOH etching and MACE demonstrates WAR of 7.5%, which is the lowest broadband reflection achieved in this work. This corresponds to potential Jsc(max) of 38.7 mA/cm2, or 13.5% enhancement compared to the Jsc(max) of the pyramids alone.
关键词： Absorption,Silver-assisted wet etching,Hybrid,Alkaline texturing
更新于2025-09-11 14:15:04
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A DLTS Perspective on Electrically Active Defects in Plated Crystalline Silicon n <sup>+</sup> p Solar Cells
摘要： Laser ablation (LA) has been compared with standard wet etching for contact opening in crystalline silicon n+p solar cells, from a perspective of electrically active defects, assessed by Deep-Level Transient Spectroscopy (DLTS). Copper metallization is employed, including a plated nickel diffusion barrier. It is shown that a hole trap around 0.17 eV above the valence band is systematically present in the depletion region of the junctions, irrespective of the contact opening method. This level could correspond with the substitutional nickel donor level in silicon and indicates that Ni in-diffusion occurs during the contact processing. No clear evidence for the presence of electrically active copper has been found. In addition, two other hole traps H2 and H3, belonging to point defects, have been observed after wet etching and standard LA, while for the highest laser power (hard LA) a broad band develops around 175 K, which is believed to be associated with dislocations, penetrating the p-type base region. Evidence will also be given for the impurity decoration of the dislocations, which enhances their electrical activity.
关键词： Deep-Level Transient Spectroscopy (DLTS),copper metallization,electrically active defects,laser ablation,nickel diffusion barrier,wet etching,crystalline silicon n+p solar cells
更新于2025-09-11 14:15:04
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An Investigation of Processes for Glass Micromachining
摘要： This paper presents processes for glass micromachining, including sandblast, wet etching, reactive ion etching (RIE), and glass reflow techniques. The advantages as well as disadvantages of each method are presented and discussed in light of the experiments. Sandblast and wet etching techniques are simple processes but face difficulties in small and high-aspect-ratio structures. A sandblasted 2 cm × 2 cm Tempax glass wafer with an etching depth of approximately 150 μm is demonstrated. The Tempax glass structure with an etching depth and sides of approximately 20 μm was observed via the wet etching process. The most important aspect of this work was to develop RIE and glass reflow techniques. The current challenges of these methods are addressed here. Deep Tempax glass pillars having a smooth surface, vertical shapes, and a high aspect ratio of 10 with 1-μm-diameter glass pillars, a 2-μm pitch, and a 10-μm etched depth were achieved via the RIE technique. Through-silicon wafer interconnects, embedded inside the Tempax glass, are successfully demonstrated via the glass reflow technique. Glass reflow into large cavities (larger than 100 μm), a micro-trench (0.8-μm wide trench), and a micro-capillary (1-μm diameter) are investigated. An additional optimization of process flow was performed for glass penetration into micro-scale patterns.
关键词： reactive ion etching,wet etching,sandblast,glass reflow process,glass micromachining
更新于2025-09-10 09:29:36
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Combined metal-assisted chemical etching and anisotropic wet etching for anti-reflection inverted pyramidal cavities on dendrite-like textured substrates
摘要： A simple and low-cost method using the combination of metal-assisted chemical etching (MacEtch) and anisotropic wet etching was performed to fabricate anti-reflection inverted pyramidal cavities on dendrite-like textured silicon substrates. To achieve this, a thin Ag film was deposited on an n-type (100) silicon substrate to form agglomerated Ag particles and MacEtch was performed to obtain vertically aligned etching holes on Si substrate. Subsequently, anisotropic wet etching was conducted and the etchant would penetrate the porous structure to form inverted pyramidal cavities on the dendrite-like structure. Using this two-step etching, excellent anti-reflection behavior was obtained for our textured substrates.
关键词： Anisotropic wet etching,Metal-assisted chemical etching,Textured substrate,Anti-reflection
更新于2025-09-10 09:29:36