Abstract Virtually complete charge transfer can be achieved with charge coupleddevices(CCDs)intheburiedchannelconfigurationbecausetheburiedchannelCCDintroduces no transfer noise. However, conventional charge detectors incorporatedinto CCDs have a comparably large noise, which consists of thermal noise and 1/fnoisefromMOS transistorin theoutputchargedetectors.
10Low-NoiseElectronicImagingwithDouble-GateFETs231
Output voltage [mV]21
0510
Packet size [electrons]15
Fig.10.16Charge/voltageconversioncharacteristicsobtainedbydiscretelevel
observation
Fig.10.17Charge/voltageconversioncharacteristics.(a)Double-gatetransistor.(b)Thin-gate-oxidetransistor(c)Thick-gate-oxidetransistor
10.2.2.4Discussion
ThedetectiontransistoristheP-channelsurfacetransistorwiththesensingchannelastheburiedgate.Here,thegateelectrodestructuresinthetransistorarediscussed.Figure10.17a–cshowssource-followerdiagramsusingthedouble-gatetransistor,athin-gate-oxidetransistor,andathick-gate-oxidetransistor,respectively.Theoxidethicknessesofthetransistorsare120and1,000nm,respectively.ThesamevoltageastheRDvoltageisappliedtotheburiedgatebyswitchingtheneighboringRSgateon.Figure10.18showstheburied-gatevoltageversustheoutputvoltageofthesourcefollowers.Thesource-followergainsareobtainedbytheslopesofcurves(a)–(c)inthe gure.Theyare0.78,0.31,and0.49,respectively.Intheburied-gatevoltagerangeof13–15V,theoutputvoltagesoftypes(a)and(b)aresaturated.
