Field-effect transistors from lithographically patterned cadmium selenide nanowire arrays

Area of Science:

• Materials Science
• Nanotechnology
• Semiconductor Physics

Background:

• Field-effect transistors (FETs) are crucial semiconductor devices.
• Nanowire field-effect transistors (NWFETs) offer potential for miniaturization and enhanced properties.
• Polycrystalline cadmium selenide (pc-CdSe) is a promising material for NWFET fabrication.

Purpose of the Study:

• To investigate the effect of CdCl(2) treatment on the properties of pc-CdSe nanowires.
• To fabricate and characterize pc-CdSe NWFETs using the lithographically patterned nanowire electrodeposition (LPNE) process.
• To analyze the influence of grain growth and crystal structure changes on NWFET performance.

Main Methods:

• Fabrication of pc-CdSe nanowires via LPNE on SiO(2)/Si substrates.
• Thermal annealing of nanowires at 300 °C for 4 hours, with and without CdCl(2) treatment.
• Characterization of nanowire structure using grazing incidence X-ray diffraction.
• Measurement of NWFET transfer characteristics (field-effect mobility, threshold voltage, subthreshold slope).

Main Results:

• CdCl(2) treatment increased mean grain diameter from 10 nm to 80 nm.
• Crystal structure converted from cubic to wurtzite following CdCl(2) treatment.
• Field-effect mobility (μ(eff)) increased by an order of magnitude (1.94 × 10(-4) to 23.4 × 10(-4) cm(2)/(V s)).
• Threshold voltage decreased from 20 V to 5 V, and subthreshold slope improved by ~35%.
• Channel length significantly affected μ(eff) in CdCl(2)-treated NWFETs, with an eight-fold reduction as length increased from 5 to 25 μm.

Conclusions:

• CdCl(2) treatment is an effective method for enhancing the performance of pc-CdSe NWFETs.
• Improved grain size and wurtzite crystal structure contribute to higher field-effect mobility and lower threshold voltage.
• Defects within nanowires, such as breaks and constrictions, impact NWFET performance, particularly at longer channel lengths.