Sangyun Lee

Effects of hydroxyl groups in polymeric dielectrics on organic transistor performance

Polymeric dielectrics having different ratios of hydroxyl groups were intentionally synthesized to investigate the effect of hydroxyl groups on the electrical properties of pentacene-based organic thin film transistors (OTFTs). Large hysteresis usually observed in OTFT devices was confirmed to be strongly related to the hydroxyl bonds existing inside of polymeric dielectrics and could be reduced by substituting with cinnamoyl groups. Although the hydroxyl groups deteriorate the capacitance-voltage characteristics and gate leakage current densities, exceptionally high hole mobility (5.5cm2V−1s−1) could be obtained by increasing the number of hydroxyl groups, which was not caused by the improvement of pentacene crystallinity but related to the interface characteristics.

The effect of moisture on the photon-enhanced negative bias thermal instability in Ga–In–Zn–O thin film transistors

We investigated the impact of photon irradiation on the stability of gallium-indium-zinc oxide (GIZO) thin film transistors. The application of light on the negative bias temperature stress (NBTS) accelerated the negative displacement of the threshold voltage (Vth). This phenomenon can be attributed to the trapping of the photon-induced carriers into the gate dielectric/channel interface or the gate dielectric bulk. Interestingly, the negative Vth shift under photon-enhanced NBTS condition worsened in relatively humid environments. It is suggested that moisture is a significant parameter that induces the degradation of bias-stressed GIZO transistors.

The Impact of Device Configuration on the Photon-Enhanced Negative Bias Thermal Instability of GaInZnO Thin Film Transistors

We investigated the effect of device configuration on the light-induced negative bias thermal instability of gallium indium zinc oxide transistors. The V th of back-channel-etch (BCE)-type transistors shifted by ―3.5 V, and the subthreshold gate swing (SS) increased from 0.88 to 1.38 V/decade after negative bias illumination temperature stress for 3 h. However, etch-stopper-type devices exhibited small V th shifts of ―0.8 V without degradation in the SS value. It is believed that the inferior instability of the BCE device is associated with the formation of an interfacial molybdenum (Mo) oxychloride layer, which occurs in the course of dry etching Mo using Cl 2 /O 2 for source/drain patterning.

The impact of SiNx gate insulators on amorphous indium-gallium-zinc oxide thin film transistors under bias-temperature-illumination stress

The threshold voltage instability (Vth) in indium-gallium-zinc oxide thin film transistor was investigated with disparate SiNx gate insulators under bias-temperature-illumination stress. As SiNx film stress became more tensile, the negative shift in Vth decreased significantly from −14.34 to −6.37 V. The compressive films exhibit a nitrogen-rich phase, higher hydrogen contents, and higher N–H bonds than tensile films. This suggests that the higher N–H related traps may play a dominant role in the degradation of the devices, which may provide and/or generate charge trapping sites in interfaces and/or SiNx insulators. It is anticipated that the appropriate optimization of gate insulator properties will help to improve device reliability.

The Effect of Passivation Layers on the Negative Bias Instability of Ga-In-Zn-O Thin Film Transistors under Illumination

Ga-In-Zn-O (GIZO) thin film transistors (TFTs) with disparate passivation structures were fabricated and their stabilities were compared. The devices were subjected to a negative bias stress with simultaneous exposure to visible light. TFT that incorporates a dual passivation composed of a SiO x layer grown at a relatively high temperature with an additional SiN x film deposited shows only -0.8 V V th shift, whereas a -5.7 V shift was observed for a TFT covered by a single SiO 2 film. The device degradation is susceptible to the ability of protecting external moisture, which may adsorb on the surface of the GIZO semiconductor to create donor states therein.

Investigation of Light-Induced Bias Instability in Hf-In-Zn-O Thin Film Transistors: A Cation Combinatorial Approach

Thin Film Transistors: A Cation Combinatorial Approach Jang-Yeon Kwon, Ji Sim Jung, Kyoung Seok Son, Kwang-Hee Lee,* Joon Seok Park, Tae Sang Kim, Jin-Seong Park, Rino Choi, Jae Kyeong Jeong, Bonwon Koo, and Sangyun Lee Display Laboratory, Samsung Advanced Institute of Technology, Nongseo-Dong, Giheung-Gu, Yongin-Si, Gyeonggi-Do 446-712, Korea Department of Materials Science and Engineering, Dankook University, Anseo-Dong, Cheonan 330-714, Korea Department of Materials Science and Engineering, Inha University, Incheon 402-751, Korea

Multilayer bipolar field-effect transistors

Field-effect transistors comprising a layer of regioregular poly(3-hexylthiophene) (rr-P3HT) separated from a parallel layer of the soluble fullerene,[6,6]-phenyl C61-butyric acid methyl ester (PCBM) by a layer of titanium suboxide (TiOx), are fabricated by solution processing. Because the TiOx is an electron transporting material and a hole blocking material, this multilayer architecture operates either in the p-channel mode with holes in the rr-P3HT layer or in the n-channel mode with electrons in the PCBM layer.

High Performance and Stability of Double-Gate Hf–In–Zn–O Thin-Film Transistors Under Illumination

Hafnium indium zinc oxide thin-film transistors (TFTs) with a double-gate structure were evaluated for the first time. Compared with devices with a single bottom gate, TFTs with an additional top gate exhibit improved subthreshold swing, threshold voltage, and field-effect mobility, as well as smaller subthreshold currents upon exposure to visible light. This phenomenon is attributed to the more effective suppression of excess photocurrents by the application of a double-gate structure. Negative-bias stress experiments under illumination indicate that the double-gate TFT exhibits very high stability compared with the device with a single-gate configuration.

A study on materials interactions between Mo electrode and InGaZnO active layer in InGaZnO-based thin film transistors

This study examined the degradation of the device performance of InGaZnO4 (IGZO)based thin-film transistors after annealing at high temperatures in air ambient. Using various characterization methods including scanning electron microscopy, x-ray diffraction, and transmission electron microscopy, we were able to disclose the details of a two-stage phase transformation that led to the device performance degradation. The Mo electrodes first succumbed to oxidation at moderate temperatures (400 500 C) and then the Mo oxide further reacted with IGZO to produce an In–Mo–O compound with some Ga at higher temperatures (600 700 C). We analyzed our results based on the thermodynamics and kinetics data available in the literature and confirmed that our findings are in agreement with the experimental results.

P-16: Integration of the 4.5″ Active Matrix Organic Light-emitting Display with Organic Transistors

We developed an active matrix organic light-emitting display(OLED) on a glass using two organic thin-film transistors(OTFTs) and a capacitor in a pixel. The OTFTs has bottom contact structure with a unique gate insulator and pentacene for the active layer. The width and length of the switching OTFT is 500 μm and 10 μm respectively and the driving OTFT has 900 μm channel width with the same channel length. The characteristics of the OTFTs were examined by test cells around display area and generated images on the panel. The mobility was 0.3 cm2V−1S−1 and the current on/off ratio was 106. The uniformity and stability were confirmed through still and moving images on the panel. The organic light-emitting layers were fabricated by shadow mask process and color fluorescence materials were used for the emitting layers. The resolution of the panel is 64×RGB×64 in 4.5 inch diagonal and the aperture ratio was 25%.