IMAGING INGAASP QUANTUM-WELL LASERS USING NEAR-FIELD SCANNING OPTICAL MICROSCOPY

The application of near-field scanning optical microscopy (NSOM) to the characterization of InGaAsP multiquantum-well lasers is reported. Collection mode images are collected at varying drive currents from well below to well above the threshold current. The high resolution of NSOM (∼λ/20) provides a detailed mapping of the laser output from the active region as well as additional output from the surrounding mesa. Spectral analysis of the image shows that the extra emission is due to InP electroluminescence. In addition to the emission characteristics of the laser it is also possible to detect local heating of the laser facet via thermal expansion. Topographical images are achieved simultaneously with NSOM images by digitizing the feedback signal which maintains a constant tip-surface gap. It is shown that these data have direct implications on device performance and problems associated with carrier leakage and nonradiative defects. © 1994 American Institute of Physics.