Nanostars in Highly Si-Doped GaN.

Area of Science:

• Materials Science
• Solid State Physics
• Semiconductor Epitaxy

Background:

• Understanding the link between surface morphology and electrical properties in Gallium Nitride with Silicon (GaN:Si) is crucial for fundamental science and applications.
• Plasma-assisted molecular beam epitaxy (PAMBE) is a key technique for growing high-quality semiconductor layers.

Purpose of the Study:

• To investigate the formation of nanostars in highly doped GaN:Si layers grown by PAMBE.
• To correlate the nanostar surface morphology with variations in electrical properties at the nanoscale.
• To elucidate the reasons behind the observed differences in etching behavior and conductivity.

Main Methods:

• Plasma-assisted molecular beam epitaxy (PAMBE) for Gallium Nitride with Silicon (GaN:Si) growth.
• Atomic Force Microscopy (AFM) and Scanning Spreading Resistance Microscopy (SSRM) for surface morphology and conductivity mapping.
• Electrochemical Etching (ECE) and Transmission Electron Microscopy (TEM) with Energy-Dispersive X-ray Spectroscopy (EDX) for structural and compositional analysis.

Main Results:

• Formation of nanostars (50-nm-wide platelets in six-fold symmetry) in highly doped GaN:Si (5 × 10^19 to 1 × 10^20 cm^-3).
• Nanostars exhibit enhanced growth along the a-direction ⟨112̅0⟩, leading to distinct surface morphology.
• Electrical property inhomogeneity at the nanoscale, with nanostars showing lower conductivity and approximately 10% less Silicon incorporation.
• Nanostars resist electrochemical etching (ECE), suggesting a compensation mechanism contributes to reduced conductivity.

Conclusions:

• Nanostar formation in highly doped GaN:Si is driven by anisotropic growth.
• Surface morphology directly influences nanoscale electrical property variations.
• A combination of lower Si content and a compensation mechanism contributes to the unique electrical characteristics of nanostars in GaN:Si.