  This paper critically examines the leakage current reduction techniques for
improving the performance of poly-Si TFTs used in active matrix liquid crystal
displays. This is a first comprehensive study in literature on this topic. The
review assesses important proposals to circumvent the leakage current problem
in poly-Si TFTs and a short evaluation of strengths and weaknesses specific to
each method is presented. Also, a new device structure called the Triple Gate
poly-Si TFT (TG-TFT) is discussed. The key idea in the operation of this device
is to make the dominant conduction mechanism in the channel to be controlled by
the accumulation charge density modulation by the gate (ACMG) and not by the
gate-induced grain barrier lowering (GIGBL). Using twodimensional and
two-carrier device simulation, it is demonstrated that the TG-TFT exhibits a
significantly diminished pseudo-subthreshold conduction leading to several
orders of magnitude reduction in the OFF state leakage current when compared to
a conventional poly-Si TFT. The reasons for the improved performance are
explained.
