Native-oxide-confined mid-IR quantum cascade lasers via non-selective oxygen-enhanced wet oxidation

Christopher S. Seibert, Mithin D'Souza, Jae C. Shin, Luke J. Mawst, Dan Botez, Douglas C. Hall

Research output: Contribution to journalConference articlepeer-review

1 Scopus citations

Abstract

In this work, a novel self-aligned process utilizing non-selective, 02-enhanced wet thermal oxidation is presented for fabricating InP-based, ridge waveguide mid-infrared (λ=5.4 μm) quantum cascade lasers (QCLs) with a strain-compensated, 30-stage (1.53 μm thick) InGaAs/AlInAs active region, grown via metal organic chemical vapor deposition. This process, previously used in GaAs-based diode lasers containing low-Al content AlGaAs or even Al-free III-As alloys, forms a highly-insulating native oxide layer while simultaneously smoothing and passivating the etch-exposed active region, resulting in low-loss, strongly-confining waveguides. Here we report the first application of this process for directly oxidizing the deeply-etched QCL InGaAs/AlInAs active region ridge waveguide sidewalls and field (outside the ridge), eliminating the need for a deposited dielectric for electrical isolation, thus allowing self-aligned device fabrication. An 8 hour, 500 °C wet oxidation with 7000 ppm added O2 (relative to N2 carrier gas) yields a uniform oxide of∼350 nm in the field outside the ridge to ∼500 nm on the ridge sidewall. Laser devices tested under room temperature, pulsed excitation exhibit a threshold current density of Jth∼3.2 kA/cm2 for a 19.5 μm wide × 3 mm long stripe width.

Original languageEnglish
Article number72301O
JournalProceedings of SPIE - The International Society for Optical Engineering
Volume7230
DOIs
StatePublished - 2009
EventNovel In-Plane Semiconductor Lasers VIII - San Jose, CA, United States
Duration: 26 Jan 200929 Jan 2009

Keywords

  • Mid-infrared
  • Nonselective wet oxidation
  • Quantum cascade laser
  • Ridge waveguide laser
  • Strain-compensated

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