High drain field impact ionization transistors as ideal switches

Area of Science:

• Semiconductor Physics
• Materials Science
• Device Engineering

Background:

• Impact ionization in transistors enables subthreshold swing below 60 mV/decade.
• Traditional silicon devices require high voltages for impact ionization, hindering low-energy operation.

Purpose of the Study:

• To demonstrate a low-voltage avalanche impact ionization phenomenon in a novel device structure.
• To achieve steep switching characteristics in silicon-based devices at reduced operating voltages.

Main Methods:

• Fabrication of a vertical subthreshold swing device using a graphene/silicon heterojunction drain and a silicon channel.
• Experimental characterization of the device's subthreshold swing and operating voltage.
• Demonstration of a complementary silicon-based logic inverter.

Main Results:

• Achieved an ultra-low average subthreshold swing of 16 µV/decade over six decades of drain current.
• Observed nearly hysteresis-free switching at an operating voltage as low as 0.4 V at room temperature.
• Demonstrated a silicon-based logic inverter with a voltage gain of 311 at a 2 V supply voltage.

Conclusions:

• The graphene/silicon heterojunction structure facilitates low-voltage avalanche impact ionization for steep switching.
• The demonstrated device offers a pathway towards highly energy-efficient semiconductor electronics.
• This technology holds potential for next-generation low-power integrated circuits.