Comparative study of contact geometry for bottom-emitting 980 nm VCSELs

R. Rosales, H. Schmeckebier, C. Boldt, P. Moser, M. E. Warren, R. F. Carson, J. A. Lott

Research output: Chapter in Book/Report/Conference proceedingConference contribution


Substrate-emitting GaAs based oxide-confined 980-nm vertical-cavity surface-emitting lasers (VCSELs) with top-surface high-frequency ground-source-ground contact pads are designed, fabricated, and characterized. The devices are composed of standard top and bottom epitaxially-grown AlGaAs distributed Bragg reflectors (DBRs). The top (p)DBR is capped with p-contact Ti then Au thin-film metals for uniform current injection and laser emission is through the GaAs substrate. The devices are realized on a single epitaxial wafer with n-ohmic-contacts placed on a thick (n+)GaAs buffer layer beneath the bottom (n)DBR and alternatively with the n-ohmic-contacts placed on an (n)GaAs intra-cavity layer lying within the same bottom (n)DBR. Static device parameters including threshold current and rollover current, differential resistance, peak optical output power, and wall-plug efficiency are extracted for VCSELs with oxide-aperture diameters ranging from about 3 to 9-μm and at different temperatures. At room temperature threshold currents are achieved from the sub-mA range up to about 3.5-mA with maximum output powers exceeding 15-mW. Increasing the temperature up to 85 °C slightly increases the threshold current while the peak output power is about halved. The differential resistance at the thermal rollover current is comparable for standard and intra-cavity n-metal-contacts. Small-signal analysis is performed for different bias currents, temperatures, oxide-aperture diameters, and the two n-contact options. Under optimal bias conditions the 3-dB bandwidth exceeds 15 GHz. Direct current modulation-based on-off keying signal generation is investigated from 10 to 40-Gb/s. The influence of an anti-reflection-coated substrate, a thinned substrate, and the combination of both is investigated and discussed.

Original languageEnglish (US)
Title of host publicationVertical-Cavity Surface-Emitting Lasers XXI
EditorsKent D. Choquette, Chun Lei
ISBN (Electronic)9781510606852
StatePublished - 2017
Externally publishedYes
EventVertical-Cavity Surface-Emitting Lasers XXI - San Francisco, United States
Duration: Feb 1 2017Feb 2 2017

Publication series

NameProceedings of SPIE - The International Society for Optical Engineering
ISSN (Print)0277-786X
ISSN (Electronic)1996-756X


ConferenceVertical-Cavity Surface-Emitting Lasers XXI
Country/TerritoryUnited States
CitySan Francisco


  • Bottom-emitting vcsels
  • Contact geometry
  • Modulation bandwidth
  • On-off keying modulation
  • Semiconductor lasers
  • Static characterization
  • Vertical-cavity surface-emitting lasers (VCSELs)

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Computer Science Applications
  • Applied Mathematics
  • Electrical and Electronic Engineering

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