The AuGe-alloy source and drain (S/D) formed on SiO2/Si(100) by the lithography process was investigated for the scaling of the organic field-effect transistors (OFETs) with bottom-contact geometry. The S/D was fabricated by the lift-off process utilizing the resist of OFPR. The OFETs with minimum channel length of 2.4 µm was successfully fabricated by the lift-off process. The fabrication yield of Au S/D was 57%, while it was increased to 93% and 100% in case of the Au-1%Ge and Au-7.4%Ge S/D, respectively. Although the mobility of the OFETs with Au-7.4%Ge S/D was decreased to 1.1×10-3 cm2/(Vs), it was able to be increased to 5.5×10-2 cm2/(Vs) by the surface cleaning utilizing H2SO4/H2O2 mixture solution (SPM) and post metallization annealing (PMA) after lift-off process, which was higher than that of OFET with Au S/D.

In this study, the effect of nitrogen-doped (N-doped) LaB6 bottom-contact electrodes and interfacial layer (IL) on n-type pentacene-based organic field-effect transistor (OFET) was investigated. The scaled OFET was fabricated by using photolithography for bottom-contact electrodes. A 20-nm-thick N-doped LaB6 bottom-contact electrodes were formed on SiO2/n+-Si(100) substrate by RF sputtering followed by the surface treatment with sulfuric acid and hydrogen peroxide mixture (SPM) followed by diluted hydrofluoric acid (DHF; 1% HF) at room temperature (RT). Then, a 1.2-nm-thick N-doped LaB6 IL was deposited at RT. Finally, a 10-nm-thick pentacene film was deposited at 100°C followed by the Al back-gate electrode formation by using thermal evaporation. The current of electron injection was observed in the air due to the effect of surface treatment and N-doped LaB6 IL.

In this research, we have investigated the deposition condition of pentacene film on nitrogen doped (N-doped) LaB6 donor layer for larger grain growth at the channel region for bottom-contact type pentacene-based organic field-effect transistors (OFETs) to improve the device characteristics. Source and drain bottom-contacts of Al were patterned and 2nm-thick N-doped LaB6 donor layer was deposited on the SiO2/Si(100) back-gate structure. The dendritic grain growth of pentacene larger than 10µm without lamellar grain growth was demonstrated when the deposition temperature and rate were 100°C and 0.5nm/min, respectively. Furthermore, it was found that the dendritic grain growth was realized at the boundary region of bottom-contact as well as channel region.