Microreflectivity studies of wavelength control in oxidised AlGaAs microcavities

R. Macaluso, F. Robert, A.C. Bryce, S. Calvez, M.D. Dawson

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1 Citation (Scopus)


Wet oxidation of GaAs/AlGaAs structures is an important technique in the processing of advanced devices such as vertical cavity surface emitting lasers (VCSELs). In one VCSEL application, the low-index and electrically-insulating AlxOy layers have been used to obtain high-reflectivity and broad bandwidth distributed Bragg reflector mirrors (DBRs). A further recent development has shown that combined lateral-vertical oxidation of intracavity AlGaAs layers can be used to tune the resonant wavelength of a semiconductor microcavity. The slow oxidation rate limits the lateral scale of practical wet oxidation to mesas structures of 50-100 m in width. Therefore post-processing assessment of spectral changes requires microreflectivity measurement capability with high spatial resolution. In the following, we describe the fabrication and assessment of microcavity structures in the 1.3 m range. The micro-reflectivity set-up consists of microscope-objective focussing of broadband light, combined with optics to relay the data to a spectrograph, and a CCD camera for alignment. This simple set-up allows the measurement of calibrated reflectivity for features down to a few 10's of m in size over a large spectral range (600-1800 nm). We present microreflectivity measurements of wide-bandwidth oxidised DBRs, and most significantly, for the first time to our knowledge, of oxidation control of the resonant wavelength of a microcavity in the 1.3 m range.
Original languageEnglish
Pages (from-to)317-322
Number of pages5
JournalMaterials Science and Engineering B
Issue number1
Publication statusPublished - 8 Feb 2003


  • microreflectivity
  • optical cavity
  • wavelength-control
  • wet oxidation


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