ELECTRICAL-PROPERTIES OF N-TYPE (111)SI IN AQUEOUS K4FE(CN)(4) SOLUTION .2. INTENSITY-MODULATED PHOTOCURRENT SPECTROSCOPY

Intensity modulated photocurrent spectroscopy (TMPS) was used to study the kinetics of recombination processes at n-type silicon surfaces in 0.1 M K4Fe(CN)(6) + 0.5 M KCl solution at pH 9. Recombination dominat es the photocurrent-potential curve at potentials up to 0.5 V positive with respect to the flatband potential in the dark. Complex plane rep resentations of the IMPS results shows almost perfect semicircles over a large potential range, indicating that surface recombination is gov erned by a single time constant process. The potential dependence and Light intensity dependence of the recombination time constant were stu died ill detail. We show that a model which incorporates the modulatio n of the potential drop across the Helmholtz laver, resulting from the modulated occupancy of the recombination centers, explains the IMPS r esults. From the results, the capacitance of the Helmholtz layer could be determined to be about 3 mu F cm(-2). The recombination rate const ant was found to be about 1 x 10(-9) cm(3) s(-1), which is in good agr eement with results from electrochemical impedance measurements.