Xingwei Ding

Improving electrical performance and bias stability of HfInZnO-TFT with optimizing the channel thickness

RF magnetron sputtered HfInZnO film and atomic layer deposition (ALD) Al2O3 film were employed for thin film transistors (TFTs) as channel layer and gate insulator, respectively. To achieve HfInZnO-TFT with high performance and good bias stability, the thickness of HfInZnO active layer was optimized. The performance of HfInZnO-TFTs was found to be thickness dependent. As the HfInZnO active layer got thicker, the leakage current greatly increased from 1.73 × 10−12 to 2.54 × 10−8 A, the threshold voltage decreased from 7.4 to −4.7 V, while the subthreshold swing varied from 0.41 to 1.07 V/decade. Overall, the HfInZnO film showed superior performance, such as saturation mobility of 6.4 cm2/V s, threshold voltage of 4.2 V, subthreshold swing of 0.43 V/decade, on/off current ratio of 3 × 107 and Vth shift of 3.6 V under VGS = 10 V for 7200 s. The results demonstrate the possibility of fabricating TFTs using HfInZnO film as active layer and using ALD Al2O3 as gate insulator.

Effect of O2 plasma treatment on density-of-states in a-IGZO thin film transistors

This work reports an efficient route for enhancing the performance of amorphous InGaZnO (a-IGZO) thin film transistors (TFT). The mobility was greatly improved by about 38% by means of O2 plasma treatment. Temperature-stress was carried out to investigate the stability and extract the parameters related to activation energy (Ea) and density-of-states (DOS). The DOS was calculated on the basis of the experimentally obtained Ea, which can explain the experimental observation. A lower activation energy (Ea, ~0.72 eV) and a smaller DOS were obtained in the O2 plasma treatment TFT based on the temperature-dependent transfer curves. The results showed that temperature stability and electrical properties enhancements in a-IGZO thin film transistors were attributed to the smaller DOS.

Enhanced photovoltaic performance of inverted polymer solar cells through atomic layer deposited Al2O3 passivation of ZnO-nanoparticle buffer layer

In this work, an atomic layer deposited (ALD) Al2O3 ultrathin layer was introduced to passivate the ZnO-nanoparticle (NP) buffer layer of inverted polymer solar cells (PSCs) based on P3HT:PCBM. The surface morphology of the ZnO-NP/Al2O3 interface was systematically analyzed by using a variety of tools, in particular transmission electron microscopy (TEM), evidencing a conformal ALD-Al2O3 deposition. The thickness of the Al2O3 layers was optimized at the nanoscale to boost electron transport of the ZnO-NP layer, which can be attributed to the suppression of oxygen vacancy defects in ZnO-NPs confirmed by photoluminescence measurement. The optimal inverted PSCs passivated by ALD-Al2O3 exhibited an ∼22% higher power conversion efficiency than the control devices with a pristine ZnO-NP buffer layer. The employment of the ALD-Al2O3 passivation layer with precisely controlled thickness provides a promising approach to develop high efficiency PSCs with novel polymer materials.

Stability enhancement in InGaZnO thin-film transistor with a novel Al2O3/HfO2/Al2O3 as gate insulator

ABSTRACT This work reports an efficient route for enhancing the stability of amorphous InGaZnO (a-IGZO) thin film transistors (TFTs). It is clearly observed that the off-current in IGZO-TFT decreases by using a novel Al2O3/HfO2/Al2O3 gate insulator. Temperature-stress measurement were carried out to investigate the stability and the parameters related to activation energy (EA) and density-of-states (DOS). The improved electrical properties are attributed to the suppression of leakage current and a lower trapping density at the channel-insulator interface. The results showed that temperature stability and electrical properties enhancements in a-IGZO thin film transistors can probably be ascribed to the smaller DOS.