Polarization effect in n-type organic non-volatile memory transistors
Sheng-Kuang Peng1, Wei-Yang Chou1*
1Department of Photonics, National Cheng Kung University, Tainan, Taiwan
* presenting author:Sheng-Kuang Peng, email:l78041169@mail.ncku.edu.tw
Organic material-based electronic devices have some individual advantages such as low-cost, low-temperature manufacturing, and structural flexibility. From the proposed organic memory device structures, organic field-effect transistor (OFET)-based memory devices have attracted many attentions because of their competitive properties, such as excellent compatibility with integrated circuits, non-destructive reading out of digital signals. In the past reports, the polymeric electrets were often used as the charge-trapping layer in OFET-based memory device, which composed of a quasi-permanent electrostatic polarization naturally. In this study, we discuss the relationship between the electrical performance of organic non-volatile memory devices (ONVMs) and the distribution of carrier trapping sites in polyimide electret. To increase the permittivity of polyimide electret and charge trapping ability of memory device, the siloxane derivatives were bonded with high polarity hydroxyl groups (which named as H3 molecules) and doped into polymer dielectric to form a polyimide electrets (PI-H3). The distribution of polar H3 molecule in polymer bulk and the surface energy of as-deposited PI film were successfully modulated by controlling the parameters of spin coating process. The typical electrical properties of n-type transistors with PI and PI-H3 electrets were measured by using a semiconductor analyzer within a nitrogen-filled box. Interestingly, the measured dielectric constant of native PI and PI-H3 film is 3.8 and 4.4, indicating that the polarization capability of PI electret was enhanced through doping polar H3 molecules in PI. From the output characteristics of ONVMs, the saturated drain current of ONVMs with PI-H3 electret as charge storage layer is obviously higher than that of the device with native PI electret. This result reveals that the electrical characteristics of ONVMs can be enhanced by the gate bias-induced dipole field to accumulate extra charge carriers at PI/semiconductor interface. Herein, we also confirm the relationships between electrical characteristics and the vertical distribution of trapping sites within polymeric electrets.
In conclusion, we demonstrate that the polar groups H3, which distributed in polymeric charge trapping layer, can govern the electrical properties and memory effects of ONVMs. This study provides a feasible route for designing high performance non-volatile transistor memory devices

Keywords: organic non-volatile memory transistors, polarization effect, charge trapping layer, polymeric electret