II-VI nanowire radial heterostructures

Area of Science:

• Materials Science
• Nanotechnology
• Semiconductor Physics

Background:

• Zinc selenide (ZnSe) nanowires exhibit poor photoluminescence due to high-temperature synthesis and unpassivated surface states.
• This results in weak band-edge emission and significant sub-bandgap defect emission.

Purpose of the Study:

• To synthesize high-quality II-VI core-shell nanowires using metal-organic vapor phase epitaxy.
• To improve the photoluminescence properties of ZnSe nanowires by passivating surface states with larger bandgap shells.

Main Methods:

• Metal-organic vapor phase epitaxy (MOVPE) for synthesizing ZnSe nanowires and ZnMgSSe shells.
• Controlled adjustment of shell reactant partial pressures to enhance passivation without increasing growth temperature.
• Photoluminescence spectroscopy to characterize material quality and emission properties.

Main Results:

• Deposition of nearly lattice-matched ZnMgSSe shells on ZnSe nanowires increased band-edge luminescence intensity by over four orders of magnitude.
• Achieved an excellent band-edge to defect photoluminescence intensity ratio of 12,000:1.
• Observed narrow full widths at half maximum (FWHM) of band-edge exciton peaks, as low as 2.8 nm.
• Demonstrated incorporation of magnesium and chlorine into ZnSe cores to tune emission wavelength and enable n-type doping.

Conclusions:

• Core-shell engineering via MOVPE is an effective strategy to overcome limitations in ZnSe nanowire photoluminescence.
• Passivation of surface states with wider bandgap shells significantly enhances luminescence efficiency and quality.
• The developed method allows for controlled tuning of optical and electrical properties of ZnSe-based nanostructures.