Structural and optical transformations by laser irradiation of InSb-based thin films

Abstract

The effect of 647 nm Kr-ion laser irradiation on small, 1 μm diameter regions of (In0.43Sb0.57)0.87Ge0.13 and In0.43Sb0.57 amorphous as-deposited thin alloy films was determined. Laser irradiation times of 50 ns-20 μs produced three distinct reflectivity states which differed from the original as-deposited values for both alloys. Both alloys exhibited an amorphous state of increased reflectivity after short pulse (∼100 ns to ∼500 ns) laser irradiation which has not been previously observed. Slightly longer pulses caused surface corrugations to form in these high reflectivity regions. The formation of corrugations was consistent with stress relaxation. Further laser annealing caused crystallization and decreased reflectivity. The addition of Ge increased the minimum time to crystallize by one order of magnitude, inhibited the precipitation of pure Sb crystals, and caused crystallites to nucleate at the spot edge rather than from the center of the spot. Optical, microstructure, and electrical changes were correlated. SEM and TEM showed that regions of similar reflectivity could result from significantly different microstructures.