| Transferable single-crystal Si nanomembranes (SiNMs) were employed in high-performance flexible electronics owing to their high intrinsic carrier mobility and material quality. An advanced pre-release-doping transfer approach was developed to minimize source/drain parasitic resistances of thin-film transistors (TFTs) to enhance their radio frequency characteristics. The high frequency characteristics of the devices were further enhanced via an overlap design between gate-source/drain, leading to a maximum oscillation frequency (fmax) of 5.5 GHz. To fully maximize the effects of pre-release SiNM doping process, effective doping for the SiNMs was performed. It was found that a low-energy implantation strategy was favored in order to achieve minimized parasitic resistance for flip-transferred SiNMs due to the fact that high doping concentration with good crystal quality has been realized after annealing. Using the optimized doping conditions, record high field effective mobility for electrons of 775 cm2/V-sec and an fmax over 10 GHz were achieved. For digital flexible electronics applications, flexible hybrid oriented SiNMs were integrated on a single plastic substrate and complementary single-crystal Si inverters integrating both Si(001) and Si(110) SiNMs were firstly realized on plastic, with good voltage transfer characteristics. Threshold voltage instability under stressing conditions and the effect of mechanical bending on the TFTs were evaluated. The transferable SiNMs were also used in fabricating photonic crystal slabs as well as transparent devices. Finally, the power handling capability of RF CMOS was investigated using dynamic load-line analysis, and an optimized strategy of voltage bias was proposed. |
