High performance transparent thin film transistors based on indium gallium zinc oxide as the channel material

The fabrication of high performance amorphous indium gallium zinc oxide (IGZO) transparent thin film transistors (TTFT) and their bias stress stability is presented. N-channel enhancement mode devices were fabricated with an extracted field effect mobility of ~ 11-15 cm
²
V
^-1
s
^-1
, on/off current ratios > 10
⁷
, subthreshold gate voltage swing of 0.20-0.25 V/decade, low off-state currents and good saturation. Low and tunable threshold voltages of 1-2 V were achieved. We conclude that a charge trapping mechanism at the semiconductor/dielectric interface is responsible for the threshold voltage shift after a gate bias stress. The threshold voltage is recovered when the bias is removed.