Current spreading structure of GaN-based vertical-cavity surface-emitting lasers.

Area of Science:

• Optoelectronics
• Materials Science

Background:

• Indium Tin Oxide (ITO) is a standard current spreading layer in Gallium Nitride (GaN)-based Vertical-Cavity Surface-Emitting Lasers (VCSELs).
• ITO's significant absorption limits laser output power, increases threshold current, and hinders ultraviolet (UV) lasing.

Purpose of the Study:

• To investigate a novel transparent conductive structure as a replacement for ITO in GaN-based VCSELs.
• To optimize the proposed structure for enhanced laser performance.

Main Methods:

• Simulated a periodic p-AlGaN/u-GaN/p-GaN structure for light-emitting diodes.
• Optimized layer parameters: 10 nm p-Al0.1Ga0.9N/2 nm u-GaN/8 nm p-GaN, combined with n-GaN/n-Al0.2Ga0.8N in the n-region.
• Applied the optimized structure to 435 nm VCSELs and compared performance against ITO-based VCSELs.

Main Results:

• The new structure reduced the threshold current density from 9.17 kA/cm² to 3.06 kA/cm².
• Laser output power increased from 1.33 mW to 15.4 mW.
• The optimized structure demonstrated significantly improved laser efficiency and power output.

Conclusions:

• The proposed periodic p-AlGaN/u-GaN/p-GaN structure is a viable and superior alternative to ITO for GaN-based VCSELs.
• This structure offers high laser power and a lower threshold, paving the way for future UV VCSEL investigations.