Temperature dependent gain characteristics in GaN-based vertical-cavity surface-emitting lasers.

Area of Science:

• Optoelectronics
• Semiconductor Physics
• Materials Science

Background:

• Vertical-cavity surface-emitting lasers (VCSELs) are key components in optical communication and sensing.
• Understanding their temperature-dependent characteristics is crucial for reliable device operation across various environments.
• InGaN/GaN multiple quantum wells are essential for achieving specific emission wavelengths in these lasers.

Purpose of the Study:

• To investigate the temperature-dependent optical gain and linewidth enhancement factor (alpha-factor) of InGaN/GaN VCSELs.
• To analyze how changes in temperature affect the carrier-dependent gain characteristics.
• To quantify the alpha-factor at different temperatures, including room temperature and cryogenic conditions.

Main Methods:

• Photoluminescence (PL) spectra measurements were performed below the threshold condition.
• The Hakki-Paoli method was employed for analyzing the gain spectra.
• Measurements were conducted across a range of temperatures, from room temperature down to 80 K.

Main Results:

• Optical gain and differential gain exhibited a more rapid increase with injected carriers as temperature decreased.
• The alpha-factor for the lasing mode was determined to be approximately 2.8 at room temperature.
• A significant reduction in the alpha-factor was observed at lower temperatures, reaching as low as 0.6 at 80 K.

Conclusions:

• Temperature has a pronounced effect on the gain characteristics and alpha-factor of InGaN/GaN VCSELs.
• Reduced operating temperatures enhance optical gain and decrease the linewidth enhancement factor, improving laser efficiency.
• These findings provide valuable insights for designing and optimizing VCSELs for high-performance applications.