Improved carrier injection in GaN-based VCSEL via AlGaN/GaN multiple quantum barrier electron blocking layer.

Area of Science:

• Optoelectronics
• Materials Science
• Semiconductor Physics

Background:

• III-nitride based vertical-cavity surface-emitting lasers (VCSELs) are crucial optoelectronic devices.
• Conventional VCSELs often utilize a bulk AlGaN electron blocking layer (EBL).
• Improving the efficiency and performance of VCSELs remains an active area of research.

Purpose of the Study:

• To demonstrate improved lasing performance in III-nitride VCSELs.
• To investigate the effect of replacing a bulk AlGaN EBL with an AlGaN/GaN multiple quantum barrier (MQB) EBL.
• To analyze the underlying mechanisms for performance enhancement.

Main Methods:

• Fabrication of III-nitride VCSELs with a conventional bulk AlGaN EBL.
• Fabrication of III-nitride VCSELs with an AlGaN/GaN MQB EBL.
• Experimental characterization of lasing performance, including output power and threshold current density.
• Theoretical calculations to understand carrier dynamics and strain effects.

Main Results:

• The output power of VCSELs with the MQB-EBL was enhanced up to three times (0.3 mW to 0.9 mW).
• The threshold current density was reduced from 12 kA/cm2 (9.5 mA) to 10.6 kA/cm2 (8.5 mA) with the MQB-EBL.
• Theoretical calculations indicated improved carrier injection efficiency due to strain release and quantum interference in the MQB structure.

Conclusions:

• Replacing the bulk AlGaN EBL with an AlGaN/GaN MQB EBL significantly improves VCSEL lasing performance.
• The MQB structure enhances carrier injection efficiency by increasing the effective conduction band barrier height.
• This approach offers a promising strategy for developing high-performance III-nitride optoelectronic devices.