There is great interest in materials for one-transistor capacitive memory elements (1T1C DRAM) based on a non-junction gate FET with high memory density. ZnO film is an interesting material for creating such memory, since dielectric properties of ZnO can be controlled by donor or acceptor impurity. The goal of this study is the investigations of the dielectric properties and mechanisms of charge carrier transport of ZnO and ZnO:Li films in wide frequency and temperature range to demonstrate the possibility of creating a memory element that combines a capacitor and a field-effect transistor. ZnO:Li dielectric layer can be used as channel of the FET and dielectric for capacitor. Proposed DRAM have good potential for memory applications because it has a high reading speed; the ratio of currents in states "1" and "0" is about 105 , and the holding time exceeds 10 ms.
We present an n-type channel transparent field-effect transistor (FET) using a top-gate configuration on a sapphire substrate. ZnO:Li film was used as channel, and MgF2 film - as gate insulator. Measurements showed that ZnO:Li films are ferroelectrics with spontaneous polarization Ps = 1–5 mkC/sm2 and coercive field EC = 5–10 kV/sm. The dependences of drain-source current on drain-source voltage at various gate-source voltages in two antiparallel Ps states were measured and the values of field-effect mobility and threshold voltage were determined for two Ps states: a) μ = 1.5 cm2/Vs, Uth = 30 V; b) μ = 1.7 cm2/Vs, Uth =23 V. Thus, Ps switching leads to a change in FET channel parameters. Results can be used to create a bistable or, more precisely, digital FET.
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