Time-domain and lock-in rate-window photocarrier radiometric measurements of recombination processes in silicon Available to Purchase

Time-domain and lock-in rate-window photocarrier radiometry (PCR) configurations are introduced both experimentally and theoretically to investigate the responses of $p$- and $n$-type Si wafers under a repetition-period-scanned square-wave-modulated super-band-gap laser beam which produces free excess photocarriers. The complete asymmetric time-domain carrier diffusion and recombination boundary-value problem with different front- and back-surface recombination velocities was solved in terms of the full spectrum of spatial eigenmodes and used to fit the time-domain data. The accurate measurement of the photocarrier transport properties (bulk lifetime, surface recombination velocities, and ambipolar diffusivity) was found to require the linear superposition of all the effective decay lifetimes associated with the eigenmode spectrum. The effects of the infinite prior pulse train to the current photocarrier radiometric response wave form were quantified and were found to be very important for certain ranges of transport parameters, pulse durations, and repetition periods. The time-domain formalism was further used to develop a theory for lock-in rate-window photocarrier radiometry. The application of the theory to the experimental results shows that they retain the time-domain character of the photocarrier generation and recombination processes, with data quality and signal-to-noise ratio superior to coaddition-averaged transients, especially in the case of samples exhibiting very low time-domain PCR signals.