Near-field scanning optical microscopy of cleaved vertical-cavity surface-emitting lasers

Near-field scanning optical microscopy (NSOM) and near-field optical spectr oscopy (NFOS) techniques have been applied to cleaved vertical-cavity surfa ce-emitting lasers (VCSELs). Collection mode NSOM of the cleaved VCSEL oper ating above the threshold current indicates emission outside the active lay er. Using the spatially resolved spectroscopy afforded by NFOS, it was poss ible to map changes in the electroluminescence spectrum with spatial resolu tion of the order of 100 nm (similar to lambda/8). The emission spectra acq uired with the tip positioned over the p-DBR layers show evidence for p-DBR luminescence. The p-DBR luminescence indicates the presence of minority ca rriers in this region of the device which have been postulated as a cause o f dark line defects (DLDs) which play an important role in device degradati on.