DETERMINATION OF EXCESS CURRENT DUE TO IMPACT IONIZATION IN POLYCRYSTALLINE SILICON THIN-FILM TRANSISTORS

Polysilicon thin-film transistors (TFTs) are of great interest for the ir circuit application in the large area microelectronics. A successfu l circuit design requires an accurate prediction of the circuit perfor mances, which in turn needs a proper modeling of the electrical device characteristics. In this present work the specific aspects of the ano malous current increase in the output characteristics, often called th e ''kink'' effect? are analysed. A new procedure to determine the exce ss current is presented and we analysed the excess current for differe nt Sate voltages, temperatures and device geometries. We show that, fr om the parameters that call be extracted by analysing a reduced set of experimental data, the excess current can be easily predicted for any bias and temperature condition and also for devices with different ge ometries; These results can be used to further up-grade the modeling o f the electrical characteristics of polysilicon TFTs in circuit simula tors. (C) 1998 Elsevier Science Ltd. All rights reserved.