NEAR-FIELD PHOTOCURRENT SPECTROSCOPY - A NOVEL TECHNIQUE FOR STUDYINGDEFECTS AND AGING IN HIGH-POWER SEMICONDUCTOR-LASERS

We present the first comparative study of spatially resolved near-fiel d photocurrent spectra for high power laser diode arrays with differen t wave guide characteristics before and after accelerated aging of the laser device. Sub-wavelength spatial resolution is demonstrated by us ing a near-field fiber probe as the excitation source. The potential o f the technique for analyzing microscopic aging processes in optoelect ronic devices is demonstrated. The experiments provide insight into me chanisms of defect formation within the p-i-n junction of InAlGaAs/GaA s laser diodes upon aging. The effect of the wave guide structure and of surface recombination processes on the near-field photocurrent imag es is discussed and analyzed in terms of a beam propagation model. The non-destructiveness makes this technique a particularly attractive me thod for in-situ analysis in high power laser diodes.