Near-field photoconductivity: Application to carrier transport in InGaAsP quantum well lasers

Abstract

A new contrast method in near-field scanning optical microscopy in which the near-field probe is used to excite photocurrent in a semiconductor sample is described and demonstrated. The use of near-field optics results in an order-of-magnitude improvement in spot size and a fivefold improvement in resolution over previous methods of photocurrent imaging. The application of this near-field photoconductivity technique to a multiquantum well laser provides direct visualization of carrier transport throughout the structure, yielding information on growth inhomogeneities, carrier leakage and isolation, and the overall quality of p-n junctions.