• Proceedings of the Korean Vacuum Society Conference
• /
• 2013.08a
• /
• pp.242.2-242.2
• /
• 2013

최근 산화물 반도체 박막 트랜지스터의 신뢰성(reliability) 평가에 대한 연구가 활발히 이루어지고 있다. 신뢰성 평가하는 한 방법으로 게이트에 바이어스를 지속적으로 인가하여 소자의 문턱 전압의 변화를 통해 안정성(stability)를 확인한다. 전압을 지속적으로 인가하게 되면 소자를 열화시켜 전기적 특성이 약화된다. 본 연구에선 ITZO 박막 트랜지스터의 신뢰성 평가를 위해 게이트 절연막($SiO_2$, $SiN_x$)에 따른 ITZO 소자를 제작 및 게이트 바이어스 스트레스 후 전기적 특성을 비교, 분석하였다. 제작된 소자의 게이트에 전압을 +15V로 7200초 동안 인가하였다. 스트레스 후 게이트 절연막이 $SiO_2$, $SiN_x$인 ITZO 산화물 박막 트랜지스터 모두 positive 방향으로 이동하였고, 그 결과 문턱 전압, 이동도, 아문턱 기울기의 변화가 발생하였다. $SiO_2$의 경우 아문턱 기울기의 변화가 거의 없이 문턱 전압의 변화만을 보였고, 이는 단순히 ITZO층과 게이트 절연막 계면에 전자가 포획되거나 혹은 게이트 절연막 내에 전자가 주입이 되었기 때문이다. 반면에 $SiN_x$의 경우 ITZO층과 게이트 절연막 계면에 추가적인 결함(defect)이 생성되었기 때문에 $SiO_2$보다 더 많은 전자를 포획하여 아문턱 기울기와 문턱 전압의 변화가 컸다.

• Korean Journal of Materials Research
• /
• v.27 no.1
• /
• pp.48-52
• /
• 2017

In this study, we used I-V spectroscopy, photoconductivity (PC) yield and internal photoemission (IPE) yield using IPE spectroscopy to characterize the Schottky barrier heights (SBH) at insulator-semiconductor interfaces of Pt/$HfO_2$/p-type Si metal-insulator-semiconductor (MIS) capacitors. The leakage current characteristics of the MIS capacitor were analyzed according to the J-V and C-V curves. The leakage current behavior of the capacitors, which depends on the applied electric field, can be described using the Poole-Frenkel (P-F) emission, trap assisted tunneling (TAT), and direct tunneling (DT) models. The leakage current transport mechanism is controlled by the trap level energy depth of $HfO_2$. In order to further study the SBH and the electronic tunneling mechanism, the internal photoemission (IPE) yield was measured and analyzed. We obtained the SBH values of the Pt/$HfO_2$/p-type Si for use in Fowler plots in the square and cubic root IPE yield spectra curves. At the Pt/$HfO_2$/p-type Si interface, the SBH difference, which depends on the electrical potential, is related to (1) the work function (WF) difference and between the Pt and p-type Si and (2) the sub-gap defect state features (density and energy) in the given dielectric.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.34 no.4
• /
• pp.246-250
• /
• 2021

TFTs technologies with as high mobility as possible is essential for high-performance large displays. TFTs using nanocrystalline silicon thin films can achieve higher mobility. In this work, the change of the crystalline volume fraction at different hydrogen dilution ratios was investigated by depositing nc-Si:H thin films using PECVD. It was observed that increasing hydrogen dilution ratio increased not only the crystalline volume fraction but also the crystallite size. The thin films with a high crystalline volume fraction (55%) and a low defect density (10¹⁷ cm^-3·eV^-1) were used as top gate TFTs channel layer, leading to a high mobility (55 cm²/V·s). We suggest that TFTs of high mobility to meet the need of display industries can be benefited by the formation of thin film with high crystalline volume fraction as well as low defect density as a channel layer.

• Laser Solutions
• /
• v.16 no.1
• /
• pp.1-4
• /
• 2013

The optical properties of III-V compound semiconductor structure was investgated by photoreflectance (PR). The results show two signals at 1.42 and 1.73eV. These are attributed to the bandgap energy of GaAs, AlGaAs, respectively. Also, AlGaAs region showed weak signal. This signal is attributed to carbon or si defect.

• Journal of the Korean Electrochemical Society
• /
• v.1 no.1
• /
• pp.40-44
• /
• 1998

The LAPS device of fast response and high sensitivity, based on electrochemical potential difference, and its system were fabricated for the precise measurement of pH changes and its characteristic were investigated. The electrostatic variation characteristics of LAPS according to the pH changes and parameters in the device were verified through a simulation using LAPS equivalent circuit model. The LAPS device and its system were fabricated on the basis of the result of simulation. The fabricated LAPS system showed linear sensitivity (about 56 mV/pH within the range of pH 2 to pH 11. In order to overcome the defect of general urea sensor (especially slow response time), urease immobilized nitrocellulose membrane was attached on the LAPS and resulted in the very fast response time, 0.29 mV/sec, 0.86 mV/sec at urea concentration of $50{\mu}g/ml,\; 500{\mu}g/ml$, respectively. And also in order to measure the uranyl ion, the uranyl ion selective sensing membrane with calix[6]arene derivative was used and its sensitivity was 25mV/concentration decade in the wide uranyl ion concentration range of $10^{-11}M\;to\;10^{-4}M$.

• Nuclear Engineering and Technology
• /
• v.54 no.3
• /
• pp.991-996
• /
• 2022

Microstructures of monolithic high purity SiC and SiC with sintering additives after neutron irradiation to a fluence of 2.0-2.5 × 10²⁴ n/m² (E > 0.1 MeV) at 333-363 K and after post-irradiation annealing up to 1673 K were observed using a transmission electron microscopy. Results showed that no black spot defects or dislocation loops in SiC grains were found after the neutron irradiation for all of the specimens owing to the moderate fluence at low irradiation temperature. Thus, it is confirmed that these specimens were swelled mostly by the formation of point defects. Black spots and small dislocation loops were discovered only after the annealing process in PureBeta-SiC and CVD-SiC, where the swelling almost diminished. Anomalous-shaped YAG grains were found in SiC ceramics containing sintering additives. These grains contained dense black spots defects and might lose crystallinity after the neutron irradiation, while these defects may annihilate by recrystallization during annealing up to 1673 K. Amorphous grain boundary phase was also presented in this ceramic, and a large part of it was crystallized through post-irradiation annealing and could affect their recovery behavior.

• Proceedings of the KIEE Conference
• /
• 2009.07a
• /
• pp.1281_1282
• /
• 2009

ICP-CVD를 이용하여 inverted staggered 구조를 갖는 미세결정 실리콘 (Nanocrystalline Silicon, nc-Si) 박막 트랜지스터(Thin Film Transistor, TFT)를 제작하였다. 또한, 소자의 특성과 전기적 안정성을 평가하였다. 실험 결과는 짧은 채널 길이를 갖는 nc-Si TFT가 긴 채널 길이의 소자보다 같은 드레인 전압 바이어스 하에서 덜 열화 됨을 알 수 있었다. 이는 드레인 전압 바이어스 하에서의 낮은 채널 캐리어 농도는 적은 defect state를 만들기 때문으로 짧은 채널 길이의 TFT가 긴 채널 길이의 TFT보다 $V_{TH}$ 열화가 적었다. 이러한 결과는 짧은 채널 길이의 nc-Si TFT가 디스플레이 분야에 있어 다양하게 응용될 것으로 기대된다.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2006.08a
• /
• pp.445-448
• /
• 2006

Bias stress effect in pentacene organic thin-flim transistors with cross-linked PVA gate dielectric is analyzed. For negative gate bias stress, positive threshold voltage shift is observed. The injected charges from the gate electrode to the defect states of gate dielectric are regarded as the main origin of $V_T$ shift. The reduced bias stress effect using $SiO_2$ blocking layer confirms the assumed mechanism. It is also demonstrated that the inverter with $SiO_2$ blocking layer shows the negligible hysteresis owing to the reduced bias stress effect.

• Korean Journal of Materials Research
• /
• v.34 no.2
• /
• pp.111-115
• /
• 2024

Silicon carbide (SiC) has emerged as a promising material for next-generation power semiconductor materials, due to its high thermal conductivity and high critical electric field (~3 MV/cm) with a wide bandgap of 3.3 eV. This permits SiC devices to operate at lower on-resistance and higher breakdown voltage. However, to improve device performance, advanced research is still needed to reduce point defects in the SiC epitaxial layer. This work investigated the electrical characteristics and defect properties using DLTS analysis. Four deep level defects generated by the implantation process and during epitaxial layer growth were detected. Trap parameters such as energy level, capture-cross section, trap density were obtained from an Arrhenius plot. To investigate the impact of defects on the device, a 2D TCAD simulation was conducted using the same device structure, and the extracted defect parameters were added to confirm electrical characteristics. The degradation of device performance such as an increase in on-resistance by adding trap parameters was confirmed.

• Journal of the Korean Vacuum Society
• /
• v.20 no.1
• /
• pp.42-49
• /
• 2011

We deposited $SiN_x$ thin films by using PECVD technique at $200^{\circ}C$ with various flow ratios of the $SiH_4/N_2$ gases. The photoluminescence measurements revealed that the maximum emission wavelength shifted to long wavelength as the ratio increased, however, positions of the several peak wavelengths, such as 1.9, 2.2, 2.4, and 3.1 eV, were independent on the ratio. Changes of the photoluminescence spectra were measured in the $N_{2}-$, $H_{2}-$, and $O_2$-annealed films. The luminescence intensities increased after the annealing process. In particular, the maximum emission wavelength shifted to short wavelength after $H_{2}-$ or $O_2$-annealing. But there were still several peaks on the spectra of all annealed films, several peak positions remained to be unchanged after the annealing. As for the light emission mechanism, we have considered the defect states of the Si- and N- dangling bonds in the $SiN_x$ energy gap, so that the energy transitions from/to the conduction/valence bands and the defect states in the gap were attributed to the light emission in the $SiN_x$ films. The experimental results point to the possibility of a Si-based light emission materials for flexible Si-based electro-optic devices.