Long-wavelength VCSELs: the case for all-epitaxial approaches

For about a decade viable vertical-cavity surface emitting lasers (VCSELs) in the short wavelength 850-980 nm range have existed based upon the lattice matched InGaAs/AlGaAs/GaAs materials system. Reasonable devices extending into the visible (/spl sim/650 nm) have also been created more recently, generally using AlInGaP active layers. In most cases, devices are grown in a single epitaxial growth step, either by MBE or MOCVD approaches. In some cases, a top dielectric mirror has been employed, but the reliability of such approaches has not been fully verified. To date, all commercially successful devices have used all-epitaxial approaches. The paper reviews recent progress with the various approaches and focus in on the issues involved in the all-epitaxial approaches. From current progress, extrapolated levels of expected performance are also presented.