Charge collection microscopy of laser annealed silicon

Silicon crystals that have been annealed by both Cw and pulsed laser irradiation have been examined by scanning, charge collection microscopy. In this technique, the short circuit current across a laser annealed diode is employed as the video signal in a scanning electron microscope, which provides a source of focused carrier injection. Repetitively pulsed, overlapping spot arrays show excellent uniformity on a scale large compared to the laser spot size, but exhibit inhomogeneity in the 1 to 10 μm range. Specifically, 1 μm ripple is observed in diodes annealed at laser powers near the surface melting of the sample surface. In well‐annealed material, the periphery of each laser spot is the region of best charge collection. Measurement of collection efficiency vs. injection depth yields estimates of carrier lifetime in the laser melted an resolidified layer. These are always small, of order 1 nsec. Finally, we have observed conversion of p‐type silicon surfaces to n‐type following CW laser annealing.