[LO phonon-plasmon coupled mode in hexagonal IngaN alloy].

Area of Science:

• Materials Science
• Solid State Physics
• Optoelectronics

Background:

• Hexagonal InGaN/GaN heterostructures are crucial for optoelectronic devices.
• Understanding their optical and electronic properties is essential for device optimization.
• Raman spectroscopy is a powerful tool for characterizing semiconductor materials.

Purpose of the Study:

• To investigate the Raman scattering spectra of hexagonal InGaN/GaN films.
• To differentiate the contributions of GaN and InGaN layers to the spectra.
• To determine key material parameters such as electron concentration and surface depletion layer thickness.

Main Methods:

• Raman spectroscopy using visible (532, 488 nm) and UV (325 nm) laser excitation.
• Temperature-dependent measurements at room temperature and 78 K.
• Analysis of phonon modes (E2, A1(LO)) and LO phonon-plasmon coupled modes.

Main Results:

• Visible laser excitation primarily probes the GaN layer (E2 ~571.3 cm⁻¹, A1(LO) ~736.4 cm⁻¹).
• UV laser excitation probes the InGaN layer, showing shifted modes (E2 ~569.7 cm⁻¹, A1(LO) ~730.3 cm⁻¹) and enhanced resonance.
• LO phonon-plasmon coupled mode in InGaN yields electron concentration (ne = 1.61 x 10¹⁸ cm⁻³) and surface depletion layer thickness (~40 nm).
• Temperature affects LO phonon-plasmon coupled mode intensity due to changes in plasmon screening and damping.

Conclusions:

• Raman spectroscopy effectively distinguishes GaN and InGaN contributions based on excitation wavelength.
• The study provides critical insights into the electronic properties of InGaN films.
• Findings support the development of advanced nitride-based optoelectronic devices.