Photomodulated reflectance as a valuable nondestructive process tool for VCSELs

Optical reflectivity spectra are useful in assessing the structure of vertical-cavity surface-emitting lasers (VCSELs) but show little of the nature of the active quantum well (QW). Here we use photomodulated reflectance to identify a region of an epitaxial wafer with optimal cavity-QW alignment. AlInGaP-AlGaAs visible VCSEL devices fabricated from this region lased well, compared with devices from a nearby control piece of the wafer which failed to lase at all.