Metal Oxide Transistors via Polyethylenimine Doping of the Channel Layer: Interplay of Doping, Microstructure, and Charge Transport. (17th June 2016) - Huang, Wei
Abstract : Polymer doping of solution‐processed In2 O3 with small amounts of the electron‐rich polymer, polyethylenimine (PEI), affords superior transistor performance, including higher electron mobility than that of the pristine In2 O3 matrix. PEI doping of In2 O3 films not only frustrates crystallization and controls the carrier concentration but, more importantly, acts as electron dopant and/or scattering center depending on the polymer doping concentration. The electron donating capacity of PEI combined with charge trapping and variation in the matrix film microstructure yields, for optimum PEI doping concentrations of 1.0%–1.5%, electron mobilities as high as ≈9 cm 2 V −1 s −1 on a 300 nm SiO2 gate dielectric, an excellent on/off ratio of ≈10 7, and an application optimal V T . Importantly, these metrics exceed those of the pure In2 O3 matrix with a maximum mobility ≈4 cm 2 V −1 s −1 . Furthermore, we show that this approach is extendible to other oxide compositions such as IZO and the technologically relevant IGZO. This work opens a new means to fabricate amorphous semiconductors via solution processing at low temperatures, while preserving or enhancing the mobility of the pristine polycrystalline semiconductor. Abstract : Enhanced metal oxide (In2 O3, IZO, IGZO) transistor performance via polyethylenimine (PEI) doping is demonstrated for the first time. Unlike previous doping methods for metal oxides, PEI doping not only effectively frustrates crystallization and controls the carrier concentration but also increases the electron mobility of the metal oxide matrix. The PEI electron donating capacity combined with charge trapping and variation in the matrix film microstructure result, for proper PEI doping levels, in high electron mobility and optimal TFT off‐currents and threshold voltages.