Logic circuits using multi-emitter resonant-tunneling hot-electron transistors (RHETs)

Developing functional devices is one way to overcome the increased wire delay and power consumption problems faced by large scale integration. The resonant-tunneling hot-electron transistor (RHET) is a functional device that features a negative differential conductance. A memory cell using resonant-tunneling diodes has been demonstrated but a logic circuit using conventional RHETs has many resistors, which limit speed and scale of integration. However, using multi-emitter RHETs a logic family can be formed which includes: a NAND/NOR gate, a NOR gate, an AND gate, an Ex-NOR gate, a data selector, latches, and flip-flops. The circuits consist of a small number of components since the multi-emitter RHET emitter electrode can be used as a base. Fabrication is less complex and the device structure more flexible than for a single-emitter RHET, because the transistor does not need a base contact. The emitter mesa etching tolerance increases and the base layer range of acceptable thicknesses and doping levels are wider. Since the multi-emitter RHETs can also function as an SRAM cell, logic circuits and SRAM cells can be integrated using the same device structure.<>