Silicon nanowire Esaki diodes.

Area of Science:

• Semiconductor Nanostructures
• Quantum Electronics
• Materials Science

Background:

• Silicon nanowires (SiNWs) are promising for advanced electronic devices.
• Tunnel diodes, specifically Esaki diodes, offer unique electrical properties.
• Understanding strain effects on semiconductor band structure is crucial for device optimization.

Purpose of the Study:

• To fabricate and characterize silicon nanowire tunnel diodes.
• To investigate the strain dependence of their electrical properties.
• To probe phonon contributions and identify impurities in the band gap.

Main Methods:

• Vapor-liquid-solid (VLS) growth of SiNWs on p-type Si substrates with in situ n-type doping.
• Electrical characterization, including current-voltage (I-V) measurements and low-temperature conductance measurements.
• Application of uniaxial tensile and compressive stress to study strain effects.

Main Results:

• Achieved Esaki diode characteristics with high peak current densities (3.6 kA/cm^2) and peak-to-valley current ratios (up to 4.3).
• Demonstrated significant strain dependence: tensile stress decreased peak current, while 1.3 GPa compressive stress increased it by 48%.
• Identified phonon peaks (transverse acoustical and optical) at 4.2 K and found no detectable gold impurities.

Conclusions:

• Silicon nanowire tunnel diodes exhibit excellent Esaki diode properties.
• The devices show a clear dependence of tunnel current on strain, reflecting Si band structure modifications.
• Phonon interactions are significant in the indirect tunneling process, and gold catalyst impurities are not detrimental.