GaSb band-structure models for electron density determinations from Raman measurements

Area of Science:

• Materials Science
• Solid State Physics
• Spectroscopy

Background:

• Accurate characterization of carrier concentration in semiconductors is crucial for device performance.
• Raman spectroscopy offers a nondestructive method for probing electronic properties.
• Gallium Antimonide (GaSb) is a key material in optoelectronics and high-speed electronics.

Purpose of the Study:

• To develop and validate Raman spectroscopy for quantifying carrier concentrations in n-type GaSb epilayers.
• To investigate the impact of different conduction-band models on carrier concentration measurements.
• To enhance the nondestructive characterization of transport properties in doped semiconductors.

Main Methods:

• Utilized Raman spectroscopy to measure coupled optical phonon-free carrier plasmon mode spectra.
• Employed the Lindhard-Mermin optical susceptibility model incorporating contributions from Γ and L conduction-band minima.
• Evaluated three conduction-band models: isotropic/parabolic, non-parabolic Γ/isotropic parabolic L, and non-parabolic Γ/ellipsoidal parabolic L minima.

Main Results:

• The model incorporating ellipsoidal L minima yielded consistently higher carrier concentrations.
• The ellipsoidal L minima model showed the best agreement with carrier-dependent mobility-ratio values derived from Hall effect measurements.
• Isotropic L minima models likely underestimate carrier concentration in GaSb at room temperature and higher doping levels.

Conclusions:

• The inclusion of ellipsoidal L minima is essential for accurate Raman-based carrier concentration measurements in n-type GaSb.
• Raman spectroscopy, when combined with appropriate band structure models, is a powerful tool for semiconductor characterization.
• Findings have implications for modeling electrical measurements and calculating electron mobility in GaSb-based devices.