Dependence of the leakage current on the film quality in polycrystalline silicon thin-film transistors

The influence of the material quality and thickness on the leakage current of polycrystalline silicon thin-film transistors is investigated. Improvement of the polycrystalline silicon layer (i.e., increase of the average grain size or decrease of the intragrain defect density) reduces only the leakage current at low electric fields in the drain region. At high electric fields, the leakage current is independent of the film quality and thickness due to the fundamental nature of the leakage current mechanisms. The experimental data indicate that Poole-Frenkel enhanced emission from traps at low electric fields and band-to-band tunneling at high electric fields are the dominant conduction mechanisms of the leakage current. (C) 2000 American Institute of Physics. [S0021-8979(00)01918-6].