• 한국정보디스플레이학회:학술대회논문집
• /
• 2007.08a
• /
• pp.904-907
• /
• 2007

We reported a simplified circuit model to investigate the interface states and the quality of a-Si film based on a MIS structure using admittance spectroscopy. The model can be employed easily to monitor the fabrication process of thin-film transistor and to obtain the important parameters.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2015.08a
• /
• pp.77.2-77.2
• /
• 2015

Recently, metamaterials attracted much attention because of the potential applications for superlens, cloaking and high precision sensors. We developed several dielectric metamaterials for enhancing antireflection or light trapping capability in solar energy harvesting devices. Colloidal lithography and electrochemical anodization process were employed to fabricate self-assembed nano- and microscale dielectric metamaterials in a simple and cost-effective manner. We improved broadband light absorption in c-Si, a-Si, and organic semiconductor layer by employing polystyrene (PS) islands integrated Si conical-frustum arrays, resonant PS nanosphere arrays, and diffusive alumina nanowire arrays, respectively. We also demonstrated thin metal coated alumina nanowire array which is utilized as an efficient light-to-heat conversion layer of solar steam generating devices. The scalable design and adaptable fabrication route to our light management nanostructures will be promising in applications of solar energy harvesting system. On the other hands, broadband invisible cloaks, which continuously work while elastically deforming, are developed using smart metamaterials made of photonic and elastic crystals. A self-adjustable, nearly lossless, and broadband (10-12GHz) smart meatamaterials have great potentials for applications in antenna system and military stealth technology.

• Current Optics and Photonics
• /
• v.5 no.2
• /
• pp.129-133
• /
• 2021

This study observed the performance of an InAs/GaSb type-II superlattice photodiode with a p-i-n structure for mid-wavelength infrared detection. The 10 ML InAs/10 ML GaSb type-II superlattice photodiode was grown using molecular beam epitaxy. The cutoff wavelength of the manufactured photodiode with Si3N4 passivation on the mesa sidewall was determined to be approximately 5.4 and 5.5 ㎛ at 30 K and 77 K, respectively. At a bias of -50 mV, the dark-current density for the Si3N4-passivated diode was measured to be 7.9 × 10-5 and 1.1 × 10-4 A/㎠ at 77 K and 100 K, respectively. The differential resistance-area product RdA at a bias of -0.15 V was 1481 and 1056 Ω ㎠ at 77 K and 100 K, respectively. The measured detectivity from a blackbody source at 800 K was calculated to be 1.1 × 1010 cm Hz1/2/W at zero bias and 77 K.

• Korean Journal of Optics and Photonics
• /
• v.3 no.4
• /
• pp.244-251
• /
• 1992

Buried Bragg filters of single mode $Si_{3}N_{4}$ rib waveguide with a cover layer of $SiO_{2}$ and grating at the interface of $Si_{3}N_{4}$ and $SiO_{2}$ are designed and fabricated. Etching of the grating on $Si_{3}N_{4}$ waveguide core by buffered HF showed uniform etching with good control up to 1 nm. This buried type of Bragg filters are immune to contamination of the surface of device. The mode index and bandwidth of filters are determined by measurements of the transmission spectrum of Bragg filters and compared with that of calculation. Waveguide Bragg filters loaded with the micro-heater of Cr film and the cladding of silicone rubber are made to control the Brag wavelength of the filter. As a result the filter wavelength of the device moved by 0.41 nm for 10 mA current to the shorter side of wavelength proportional to the square of the current.

• Journal of IKEEE
• /
• v.24 no.2
• /
• pp.409-418
• /
• 2020

In this paper, an integrated optical, evanescent-wave biosensor utilizing a multimode interferometer based on a Si₃N₄ rib-optical waveguide consisting of the Si/SiO₂/Si₃N₄/SiO₂ stacked structure was described. The theoretical background of the multimode interferometer was reviewed, and the structure and design process were presented through numerical computational analysis. We analyzed how the dimension (length, width) of the multimode interferometer affected the sensor performance. It has been confirmed through computational analysis that the changes in the refractive index of an analyte greatly affect the mode pattern formation position and output optical power of a multimode interferometer, and proved that this principle could be applied to integrated-optic biosensor.

• Journal of the Optical Society of Korea
• /
• v.17 no.5
• /
• pp.433-440
• /
• 2013

We present an experimental and numerical study of spectral profiles of effective group indices of hydrogenated amorphous silicon (a-Si:H) waveguides and of their chromatic-dispersion effect on the four-wave-mixing (FWM) signal generation. The a-Si:H waveguides of 220-nm thickness and three different widths of 400, 450 and 500 nm were fabricated by using the conventional CMOS device processes on a $2-{\mu}m$ thick $SiO_2$ bottom layer deposited on 8-inch Si wafers. Mach-Zehnder interferometers (MZIs) were formed with the a-Si:H waveguides, and used for precise measurement of the effective group indices and thus for determination of the spectral profile of the waveguides' chromatic dispersion. The wavelength ranges for the FWM-signal generation were about 45, 75 and 55 nm for the 400-, 450- and 500-nm-wide waveguides, respectively, at the pump wavelength of 1532 nm. A widest wavelength range for the efficient FWM process was observed with the 450-nm-wide waveguide having a zero-dispersion near the pump wavelength.

• Korean Journal of Optics and Photonics
• /
• v.3 no.1
• /
• pp.50-54
• /
• 1992

Maskless depositon of copper onto n-doped and p-doped Si in an aqueous copper sulfate solution is investigated. On p-doped Si substrates, microscopic $(~10\mu\textrm{m}$) copper spots are deposited by illuminating continuous wave $Ar^+$ laser beam of wavelength 514.5 nm. Copper deposition on n-doped Si substrates is also achieved by shinning second harmonic pulses $(pulse width~25 nsec, \lambda=530 nm)$ of a passively Q-switched Nd:YAG laser. The observed deposition is attributed to the electric field resulting from the Galvanic potential of a semiconductor-electrolyte junction.

• Korean Journal of Optics and Photonics
• /
• v.13 no.5
• /
• pp.396-399
• /
• 2002

Using a bi-layer anti-reflection coating of $TiO_2$and $SiO_2,$ we have achieved a minimum facet reflectivity of $~10^{-5}$ and a band width of 27 nm for a reflectivity of $~10^{-4}$ or less for 1.3 $\mu\textrm{m}$ spot size converter integrated semiconductor lasers. This coating is applicable to external-cavity-tuned laser sources and semiconductor optical amplifiers.

• Progress in Superconductivity
• /
• v.8 no.2
• /
• pp.181-185
• /
• 2007

For more than two decades Nb trilayer ($Nb/Al_2O_3/Nb$) process has been serving as the most stable fabrication process of the Josephson junction integrated circuits. Fast development of semiconductor fabrication technology has been possible with the recent advancement of the fabrication equipments. In this work, we took an advantage of advanced fabrication equipments in developing a superconducting Arithmetic Logic Unit (ALU) by using Nb trilayers. The ALU is a core element of a computer processor that performs arithmetic and logic operations on the operands in computer instruction words. We used DC magnetron sputtering technique for metal depositions and RF sputtering technique for $SiO_2$ depositions. Various dry etching techniques were used to define the Josephson junction areas and film pattering processes. Our Nb films were stress free and showed the $T{_c}'s$ of about 9 K. To enhance the step coverage of Nb films we used reverse bias powered DC magnetron sputtering technique. The fabricated 1-bit, 2-bit, and 4-bit ALU circuits were tested at a few kilo-hertz clock frequency as well as a few tens giga-hertz clock frequency, respectively. Our 1-bit ALU operated correctly at up to 40 GHz clock frequency, and the 4-bit ALU operated at up to 5 GHz clock frequency.

• Journal of the Optical Society of Korea
• /
• v.18 no.5
• /
• pp.569-573
• /
• 2014

We demonstrate a low-cost, superbly efficient way of etching for the nano-, and micro-sized pyramid patterns on (100)-oriented Si wafer surfaces for use as a patterned master. We show a way of producing functional optical films for the viewing angle direction brightness-enhancement of Lambertian LED (light emitting diode)/OLED (organic light emitting diode) planar lighting applications. An optimally formulated KOH (Potassium hydroxide) wet etching process enabled random-positioned, and random size-distributed (within a certain size range) pyramid patterns to be developed over the entire (100) silicon wafer substrates up to 8" and a simple replication process of master patterns onto the PC (poly-carbonate) and PMMA (poly-methyl methacrylate) films were performed. Haze ratio values were measured for several film samples exhibiting excellent values over 90% suitable for LED/OLED lighting purposes. Brightness was also improved by 13~14% toward the viewing angle direction. Computational simulations using LightTools$^{TM}$ were also carried out and turned out to be in strong agreement with experimental data. Finally, we could check the feasibility of fabricating low-cost, large area, high performance optical films for commercialization.