METAL (COSI2)/INSULATOR (CAF2) HOT-ELECTRON TRANSISTOR FABRICATED BY ELECTRON-BEAM LITHOGRAPHY ON A SI SUBSTRATE

We fabricated a small-area metal (CoSi2)/insulator (CaF2) hot electron transistor using electron-beam lithography. The transistor is composed of a CoSi2/CaF2(1.9 nm)/CoSi2(1.9 nm) tunnel emitter and a CaF2(5 nm) collector barrier on an n-Si(111) substrate. The emitter mesa area is 0.9 x 0.9 mu m(2). Although the measured characteristics show, for the first time, clear transistor action with a curve similar to those of semiconductor HETs: the collector current increases without saturation due to leakage current through the SiO2 film under the external electrode pads. The intrinsic device characteristics (zero leakage current) exhibited saturation, and a current gain beta greater than or equal to 36 was obtained at 77 K.