More Like this

1. Demonstration of 4H-silicon carbide on an aluminum nitride integrated photonic platform

   https://doi.org/10.1364/OL.521157  

   Wang, Ruixuan; Li, Jingwei; Cai, Lutong; Li, Qing (January 2024, Optics Letters)

   The existing silicon-carbide-on-insulator photonic platform utilizes a thin layer of silicon dioxide under silicon carbide (SiC) to provide optical confinement and mode isolation. Here, we replace the underneath silicon dioxide layer with 1-µm-thick aluminum nitride and demonstrate a 4H-silicon-carbide-on-aluminum-nitride integrated photonic platform for the first time to our knowledge. Efficient grating couplers, low-loss waveguides, and compact microring resonators with intrinsic quality factors up to 210,000 are fabricated. In addition, by undercutting the aluminum nitride layer, the intrinsic quality factor of the silicon carbide microring is improved by nearly one order of magnitude (1.8 million). Finally, an optical pump–probe method is developed to measure the thermal conductivity of the aluminum nitride layer, which is estimated to be over 30 times of that of silicon dioxide. 

   more » « less
2. Transmission Electron Microscopy Characterizations of Local Amorphization of Single Crystal Silicon by Nanosecond Pulsed Laser Direct Writing

   https://doi.org/10.1002/adem.202301377  

   Trinh, Lanh; Wang, Xinya; Zhang, Xiang; Hosseini-Zavareh, Sajed; Mao, Aofei; Yu, Xiaoming; Lei, Shuting; Cui, Bai (December 2023, Advanced Engineering Materials)

   The concept for fabrication of waveguides by an in‐volume laser direct writing in single‐crystal silicon is explored using a nanosecond pulse laser. The key innovation of this technology relies on the generation of amorphous silicon, which has a higher refractive index than that of crystalline silicon. Herein, transmission electron microscopy (TEM) together with selected area electron diffraction (SAED) and high‐resolution TEM (HRTEM) characterizations are used to better understand the microstructural evolutions. TEM images reveal the core‐shell structures, while SAED patterns and HRTEM directly observe the presence of amorphous silicon in the core surrounded by a crystalline silicon shell. With a lower laser scanning speed, a higher density of defects yet less amorphous silicon is formed by laser direct writing. 

   more » « less
3. Shallow Si N + P junction diodes realized via molecular monolayer doping

   https://doi.org/10.1016/j.mee.2018.02.008  

   Astha Tapriya, Brian Novak (January 2022, Microelectronic engineering)

   Lanza, Mario (Ed.)

   A conformal and controlled semiconductor doping is needed for applications in next generation nanoscale devices,low contact resistivity metal semiconductor junctions such as selective emitters in solar cells. Molecular monolayer doping (MLD) in silicon is a novel technique based on the formation of self-assembled monolayer of dopant – containing molecules on surface of crystalline silicon, followed by rapid thermal anneal. The technique is capable of forming ultra-shallow junctions with high atomic accuracy and minimum defects in silicon. A container and process was developed which successfully doped 6 in. diameter silicon wafers using MLD for the in-house CMOS fabrication facility. The phosphorus monolayer is grafted on hydrogen terminated p-type silicon followed by rapid thermal anneal. Average sheet resistance ~670 Ω/sq. and junction depth ~25 nm are achieved. N + P junctions are fabricated using MLD and current-voltage characteristics are measured and analyzed using unified diode model. 

   more » « less
4. Spectroelectrochemical and Theoretical Study of [Si(ttpy)2](PF6)4: A Potential Polychromatic Electrochromic Dye

   https://doi.org/10.3390/molecules27238521  

   Peloquin, Derek M.; Bimukhanov, Askhat N.; Aldongarov, Anuar A.; Merkert, Jon W.; Donovan-Merkert, Bernadette T.; Schmedake, Thomas A. (December 2022, Molecules)

   Complexes consisting of earth-abundant main group metals such as silicon with polypyridine ligands are of interest for a variety of optical and electronic applications including as electrochromic colorants. Previous spectroelectrochemical studies with tris(2,2′-bipyridyl)silicon(IV) hexafluorophosphate, [Si(bpy)3](PF6)4, demonstrated an ability to control the color saturation of the potential electrochromic dye, with the intensity of the dye’s green color increasing as the charge state sequentially reduces from 4+ to 1+. In this study, the synthesis of bis(4′-(4-tolyl)-2,2′:6′,2″-terpyridine)silicon(IV) hexafluorophosphate, [Si(ttpy)2](PF6)4, is reported along with electrochemical and spectroelectrochemical analyses. Computational modeling (density functional theory) is used to further elucidate the electrochromic properties of previously reported Si(bpy)3n+ species and the new Si(ttpy)2n+ species. While the homoleptic tris(bidentate)silicon(IV) complexes are attractive as electrochromic dyes for tunable color saturation, the bis(tridentate)silicon(IV) complexes are attractive as polychromatic electrochromic dyes. 

   more » « less
5. Silicon‐On‐Silicon Carbide Platform for Integrated Photonics

   https://doi.org/10.1002/adom.202401101  

   DeVault, Clayton_T; Deckoff‐Jones, Skylar; Liu, Yuzi; Hammock, Ian_N; Sullivan, Sean_E; Dibos, Alan; Sorce, Peter; Orcutt, Jason; Awschalom, David_D; Heremans, F_Joseph; et al (August 2024, Advanced Optical Materials)

   Abstract Silicon carbide (SiC)'s nonlinear optical properties and applications to quantum information have recently brought attention to its potential as an integrated photonics platform. However, despite its many excellent material properties, such as large thermal conductivity, wide transparency window, and strong optical nonlinearities, it is generally a difficult material for microfabrication. Here, it is shown that directly bonded silicon‐on‐silicon carbide can be a high‐performing hybrid photonics platform that does not require the need to form SiC membranes or directly pattern in SiC. The optimized bonding method yields defect‐free, uniform films with minimal oxide at the silicon–silicon–carbide interface. Ring resonators are patterned into the silicon layer with standard, complimentary metal–oxide–semiconductor (CMOS) compatible (Si) fabrication and measure room‐temperature, near‐infrared quality factors exceeding 10⁵. The corresponding propagation loss is 5.7 dB cm⁻¹. The process offers a wafer‐scalable pathway to the integration of SiC photonics into CMOS devices. 

   more » « less