Improved Performance of Pentacene OTFT with HfLaO Gate Dielectric by Annealing in NH3

Abstract

Pentacene organic thin-film transistors with HfLaO as gate dielectric were fabricated. The dielectric was prepared by sputtering method with a dielectric constant over 11, and hence the OTFTs could operate at a voltage less than 5 V. The dielectric was annealed in N2, NO or NH3 at 400 oC after sputtering to passivate the surface of the dielectric. The OTFT treated in NH3 displayed higher carrier mobility, smaller sub-threshold swing, and lower 1/f noise than the OTFTs annealed in N2 and NO respectively. SEM image indicated that pentacene inclined to form larger grains on the dielectric annealed in NH3 than the dielectric annealed in N2 or NO. The enhanced electrical performance of OTFTs annealed in NH3 can be attributed to the improved interfacial characteristics between the organic film and the gate dielectric.