Tunnelling Hot Electron Transfer Amplifier Device With Reduced Input Capacitance
Original Publication Date: 1988-Sep-01
Included in the Prior Art Database: 2005-Feb-15
Low input capacitance of tunnelling hot electron transfer amplifier (THETA) devices is achieved by maintaining the thickness of the tunnelling barrier fixed while reducing the dopant concentration. Referring to the figure, the base region of a THETA device has a tunnel emitter 1 with a thickness of 50-100 Ao, an undoped region 2 of thickness approximately 500 Ao, and a heavily doped region 3 with a thickness 200-400 Ao . Since ballistic electrons can pass through relatively thick base regions with low dopant concentrations, base thickness can be made larger by keeping the doped region far from the tunnelling emitter. A major portion of the base-emitter voltage is across the undoped region, so that tunnelling current can be increased by reducing the barrier thickness to improve tunnelling probability, even at low voltages.