Challenges and advancement of blue III-nitride vertical-cavity surface-emitting lasers

Chia-Yen Huang*, Kuo Bin Hong, Zhen Ting Huang, Wen Hsuan Hsieh, Wei Hao Huang, Tien Chang Lu

*Corresponding author for this work

Research output: Contribution to journalReview articlepeer-review

Abstract

Since the first demonstration of (Al, In, Ga)N-based blue vertical-cavity surface-emitting lasers (VCSELs) in 2008, the maximum output power (Pmax) and threshold current density (Jth) has been improved significantly after a decade of technology advancements. This article reviewed the key challenges for the realization of VCSELs with III-nitride materials, such as inherent polarization effects, difficulties in distributed Bragg’s reflectors (DBR) fabrication for a resonant cavity, and the anti-guiding effect due to the deposited dielectrics current aperture. The significant tensile strain between AlN and GaN hampered the intuitive cavity design with two epitaxial DBRs from arsenide-based VCSELs. Therefore, many alternative cavity structures and processing technologies were developed; for example, lattice-matched AlInN/GaN DBR, nano-porous DBR, or double dielectric DBRs via various overgrowth or film transfer processing strategies. The anti-guiding effect was overcome by integrating a fully planar or slightly convex DBR as one of the reflectors. Special designs to limit the emission polarization in a circular aperture were also summarized. Growing VCSELs on low-symmetry non-polar and semipolar planes discriminates the optical gain along different crystal orientations. A deliberately designed high-contrast grating could differentiate the reflectivity between the transverse-electric field and transverse-magnetic field, which restricts the lasing mode to be the one with the higher reflectivity. In the future, the III-nitride based VCSEL shall keep advancing in total power, applicable spectral region, and ultra-low threshold pumping density with the novel device structure design and processing technologies.

Original languageEnglish
Article number676
Number of pages19
JournalMicromachines
Volume12
Issue number6
DOIs
StatePublished - Jun 2021

Keywords

  • Carrier aperture
  • Distributed Bragg reflector
  • GaN
  • III-nitrides
  • Polarization
  • VCSEL

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