MICROWAVE DETECTION OF MINORITY-CARRIERS IN SOLAR-CELL SILICON-WAFERS

Techniques measuring photoconductive decay by means of microwaves (mu- PCD) can be used to detect free carriers in semiconductors. The instru ment as developed at ECN for characterization of the solar cell materi al is described. The experimental details of two measurement technique s and the theoretical background are discussed. In the decay method th e effective mean lifetime of the minority carriers is measured. In the harmonic modulation technique information about the lifetime of the m inorities is contained in the phase-shift of the microwave signal rela tive to the phase of the light intensity. The aim of this research is to determine the bulk mean lifetime of the minority carriers and the s urface recombination velocities of solar cell silicon wafers by a non- destructive and contactless technique. Typical experiments will be pre sented.