Metal-semiconductor. field-effect. transistors.(MESFET). are. commonly. known. from. GaAs. technology.[1]. and. are. widely. used. for. high-speed. logic. circuits. due. to. their. high. channel. mobility.[2, 3].. In. contrast. to. GaAs-MESFET,. which. consist. of. an. n-type. implanted. channel. in. a. p-type. or. semi-insulating. GaAs. substrate,. oxide. MESFET. consist. of. a. thin. semiconducting. channel. layer. on. an. insulating. substrate.(Figure. 11.1 a).. Their. gate. structure. is. a. rectifying. Schottky. contact.(SC).. However,. this. technology. is. a. rather. new. subject. in. the. ZnO. community. and. in. transparent. electronics.. Since. the. p-type. doping. of. ZnO. and. consequently. the. fabrication. of. bipolar. devices. still. remains. a. challenge,. unipolar. devices. become. more. and. more. interesting.. For. ZnO. thin. films,. the. MESFET. technology. was. demonstrated. some. years. ago. by. Ryu. et. al.,. who. used. a. Ti-gate. contact. on. p-type. ZnO.[4].. Later,. Kandasamy. et. al.. used. Pt-gate. n-ZnO. MESFET. for. hydrogen. gas. sensing.[5],. and. Kao. et. al.. used. Pt/Au-gate. contacts. for. their. MESFET.[6].. However,. these. reported. thin-film. ZnO. MESFET. showed. inferior. electronic. properties. with. high. gate. voltage. sweeps. between. 4. and. 20. V,. very. low. on/off-ratios. below. 10,. and. barely. obtained. pinch-off. and. saturation. behavior.. On. the. basis. of. ZnO. nanorods,. MESFET. and. logic. devices. such. as. OR,. AND,. NOT,. and. NOR. gates. have. been. realized. by. Park. et. al.. using. Au-gate. contacts.[7].. Their. on/off-ratio. was. approximately. 104. and. a. subthreshold. slope. between. 100. and. 200. mV/decade. was. achieved.. However,. channel. mobilities. were. neither. reported. for. ZnO. thin. film. nor. nanorod. MESFET. ZnO-MESFET. performance. advanced. significantly. in. 2008. by. using. AgxO-gated. MESFET. as. demonstrated. by. Frenzel. et. al.. showing. an. on/off-ratio. of. 108,. a. gate-voltage. sweep. of. only. 3. V,. and. a. channel. mobility. of. 11.3. cm2/(Vs).[8].. Since. then,. ZnO-based. MESFET. have. been. improved,. especially. with. regard. to. their. applicability. in. low-cost. transparent. electronics.[9].. However,. in. transparent. electronics,. still. the. established. technology. of. metal–insulator–semiconductor. field-effect. transistors.(MISFET). is. used.. Currently,. there. are. several. approaches. for. transparent. MISFET,. which. are. assigned. to. substitute. amorphous-Si. transistors. in. backplanes. of. active-matrix. displays:. carbonnanotube. FET.(CNTFET),. organic. FET.(OFET),. and. transparent-oxide. MISFET.(TMISFET).. The. different. technologies. are. compared. in. Table. 11.1.. Single. CNT. promise. a. high. channel. mobility. of. 3000. cm2/(Vs).[10].. They. are. fabricated,. however,. by. means. of. complex. laser-based,. plasma-based,. or. chemical. processes,. for. example,. chemical. vapor. deposition.. CNT-networks. can. then. be. deposited. from. solution. on. large. substrates. at. low. temperatures. to. create. CNTFET.[11].. The. channel. mobilities. of. such. transistors. are. only. in. the. range. of. 0.5–30. cm2/(Vs). due. to. interface. effects. and. the. highly. disordered. structure.