Metal (CoSi 2)/Insulator (CaF 2) 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 × 0.9 µm2. 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 β ≥ 36 was obtained at 77 K.