High current density heterojunction bipolar transistors with 3D-GaN/2D-WSe₂ as emitter junctions

Area of Science:

• Materials Science
• Electrical Engineering
• Nanotechnology

Background:

• Increasing demand for high-speed, high-frequency, and high-power electronic devices.
• Two-dimensional (2D) layered materials (2DLMs) offer advantages for heterojunction bipolar transistors (HBTs) due to their thinness and lack of dangling bonds.
• Current limitations in 2DLM-based HBTs include low current density and restricted structural design.

Purpose of the Study:

• To introduce a novel vertical Gallium Nitride (GaN)/Tungsten Diselenide (WSe₂)/Molybdenum Disulfide (MoS₂) heterojunction bipolar transistor (HBT).
• To overcome the limitations of existing 2DLM-based HBTs by enhancing current density and structural design flexibility.

Main Methods:

• Fabrication of a vertical HBT structure utilizing a three-dimensional (3D)-GaN/2D-WSe₂ heterojunction as the emitter junction.
• Integration of MoS₂ as a key component within the HBT architecture.
• Strategic placement of the collector electrode to optimize carrier collection efficiency.

Main Results:

• Achieved a high current density of approximately 260 A cm^-2 by leveraging the properties of 3D-GaN.
• Obtained a common-base current gain of 0.996.
• Demonstrated a significant common-emitter current gain (β) of 12.4 due to efficient carrier collection.

Conclusions:

• The novel vertical GaN/WSe₂/MoS₂ HBT design successfully addresses the limitations of previous 2DLM-based devices.
• The device exhibits promising performance metrics, including high current density and substantial current gain.
• This advancement paves the way for next-generation high-performance electronic applications.