Absorption tail analysis by spectroscopic ellipsometry: a reduced-parameter approach to electric field...

Area of Science:

• Materials Science
• Optoelectronics
• Solid State Physics

Background:

• Non-invasive characterization of electric fields is crucial for semiconductor and photonic devices.
• Conventional methods like Franz-Keldysh (FK) oscillation spectroscopy have limitations in field configuration and require modulation.
• Accurate electric field mapping is essential for optimizing device performance and understanding charge dynamics.

Purpose of the Study:

• To introduce a novel, universally applicable optical method for in situ electric field characterization.
• To simplify the complex fitting problem in optical characterization by reducing free parameters.
• To establish a practical platform for real-time optical field diagnostics in various device architectures.

Main Methods:

• Utilizing spectroscopic ellipsometry to analyze the absorption tail of materials.
• Exploiting the intrinsic equivalence between the broadening factor (γ) and space-charge region width (L) to reduce fitting parameters.
• Validating the method on Si-doped GaN single crystals with varying carrier densities.

Main Results:

• Demonstrated a significant reduction in root mean square error (up to 68.7%±41.2%) compared to traditional methods.
• Showcased the method's universal applicability across narrow/wide and uniform/non-uniform electric field configurations.
• Confirmed the convergence of γ to zero for L > 90 nm, simplifying analysis.

Conclusions:

• The developed method offers a practical and accurate approach for in situ electric field diagnostics.
• Its material-general nature and compatibility with external stimuli make it ideal for advanced semiconductor and photonic devices.
• This technique overcomes limitations of conventional methods, enabling broader application in device research and development.