Dark current in selectively doped N-AlGaAs/GaAs CCDs

The dark current of Schottky-barrier gate charge-coupled devices (CCDs) utilizing selectively doped N-AlGaAs/GaAs structures grown by molecular beam epitaxy was investigated. The generation rate of carriers in the CCD channel, i.e. the dark current, and its temperature dependence were measuredin detail. The dark current was dominated by the reverse current of the Schottky barrier gate and consisted of the reverse current of the operating gate as well as that of the neighboring two gates. Thereverse current was shown to be dominated either by the thermionic-field emission current or by the field emission current because of the high doping of AlGaAs. A measure of the reduction of the reversecurrent is also presented.