| AVS 58th Annual International Symposium and Exhibition | |
| Transparent Conductors and Printable Electronics Focus Topic | Thursday Sessions |
| Session TC+EM+NS-ThA |
| Session: | Transparent / Printable Electronics Part 2 |
| Presenter: | DongHee Lee, Tokyo Institute of Technology, Japan |
| Authors: | D.H. Lee, Tokyo Institute of Technology, Japan K. Nomura, Tokyo Institute of Technology, Japan T. Kamiya, Tokyo Institute of Technology, Japan H. Hosono, Tokyo Institute of Technology, Japan |
| Correspondent: | Click to Email |
Amorphous oxide semiconductors (AOSs) are expected as an alternative to amorphous/poly-Si for thin-film transistors (TFTs) in next-generation flat-panel displays (FPDs) because AOS TFTs have many advantages such as large field-effect mobilities (>10 cm2(Vs)-1) and low-temperature process [1]. For more advancing AOS optoelectronic technology, it is important to develop more various devices other than TFTs, and to study some remaining issues such as operation characteristics of AOS devices under light illumination.
In this study, we fabricated good and stable metal-AOS Schottky contacts made of amorphous In-Ga-Zn-O (a-IGZO) and bottom Pt electrodes at temperatures below 200oC even though it is generally difficult to make high performance oxide Schottky junctions [2]. It was found that the a-IGZO/Pt Schottky contacts have an ideality factor n ~ 1.1 and a Schottky barrier height фb ~ 0.9 eV, which were evaluated from their J-V curves using the thermionic emission model. From C-V results, the Schottky junctions operate at the full-depletion condition, whose C corresponds to the geometrical capacitance of the a-IGZO layer, and relative permittivity εs of a-IGZO was obtained approximately 13. However, the results of temperature dependences of J-V characteristics were unexplained if we take a simple uniform Schottky barrier model; we found that the barrier potential fluctuations model [3] explained them well, and the mean barrier height фb, m of 1.2 eV and the net electron affinity χs of a-IGZO of 4.2 eV were obtained. On the other hand, the Schottky contacts showed very small open circuit voltages (VOC’s) < 0.1 V under 100 mWcm-2 AM1.5 light illumination, which are far smaller than the built-in potential (Vbi ~ 0.4 eV) estimated from the C-V measurements in dark. We also observed that VOC decays with time after starting the light illumination. We will discuss the mechanism of the small VOC based on these results.
[1] T. Kamiya et. al. Sci. Technol. Adv. Mater. 11 044305 (2010).
[2] K. Ip et al., J. Cryst. Growth 287, 149 (2006).
[3] J. H. Werner and H. H. Güttler, J. Appl. Phys. 69, 1522 (1991).