Optical near-field photocurrent spectroscopy as a new tool for analyzing optoelectronic devices

Optical near-field spectroscopy and related methods display a rapid development as powerful new analytical tools for the investigation of optoelectronic devices such as, e.g., semiconductor lasers. Photocurrent spectroscopy, belonging to the traditional methods of semiconductor physics, gained an entirely new range of application by employing an optical near-field microscope as the optical excitation source. Thus near-field optical beam induced current (NOBIC) spectroscopy has been developed. It combines the spatial resolution of less than some 100 nm of electron beam based techniques such as electron beam induced current (EBIC) with the advantages of providing selective excitation of the laser structure if a tunable wavelength excitation source is used and being completely non-destructive. Here, a NOBIC study of different GaAs-AlGaAs high power diode laser array structures such as double quantum well (DQW) graded index separate confinement heterostructures as well as step index AlGaAs structures is presented.