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. Improveme nt of the polycrystalline silicon layer (i.e., increase of the average grai n size or decrease of the intragrain defect density) reduces only the leaka ge current at low electric fields in the drain region. At high electric fie lds, the leakage current is independent of the film quality and thickness d ue to the fundamental nature of the leakage current mechanisms. The experim ental 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 In stitute of Physics. [S0021-8979(00)01918-6].