Practical Issues for Atom Probe Tomography Analysis of III-Nitride Semiconductor Materials

Area of Science:

• Materials Science
• Semiconductor Physics
• Analytical Chemistry

Background:

• Atom probe tomography (APT) is crucial for nanoscale material characterization.
• III-nitride semiconductors are vital for electronic and optoelectronic devices.
• Challenges exist in preparing and analyzing these materials with APT.

Purpose of the Study:

• To investigate practical issues in APT analysis of III-nitride semiconductors.
• To optimize specimen preparation and data acquisition parameters.
• To understand and mitigate artifacts in APT data.

Main Methods:

• Focused ion beam (FIB) microscopy for specimen preparation using a mono-isotopic Ga source.
• Atom probe tomography (APT) analysis in both pulsed laser and pulsed voltage modes.
• Examination of reconstructed InAlN/GaN heterostructures.

Main Results:

• Identified and quantified Ga implantation damage during FIB preparation.
• Demonstrated significant reduction of Ga implantation by lowering the clean-up voltage (5 kV to 1 kV).
• Observed monotonic increase in measured Ga content with laser pulse energy and voltage pulse fraction.
• Achieved near-stoichiometric Ga content and clear crystallographic structure at low laser energy.

Conclusions:

• Lowering FIB voltage is critical for minimizing Ga implantation artifacts in III-nitride APT.
• Optimized APT parameters (low laser energy, specific voltage pulse fraction) yield accurate chemical composition and structural information.
• This study provides essential guidelines for reliable APT analysis of InAlN/GaN heterostructures.