Fabrication of large-grain polycrystalline Ge films using absorptive films

Amorphous germanium (a-Ge) films in samples with or without an absorptive film are crystallized by short-pulse XeF excimer laser crystallization (ELC). An in situ time-resolved optical reflection and transmission (TRORT) monitoring system combining a cw He-Ne probe laser, a digital oscilloscope and two photodetectors is developed to investigate the melting and resolidification dynamics of Ge films during ELC. TRORT measurements reveal that the longest melt duration is prolonged from 250 to 1000 ns by adding absorptive films in the samples. Absorptive films are shown to be effective in improving the melt duration of the molten state and the grain size of polycrystalline Ge films. The grain size with a diameter of approximately 12 μm can be fabricated in the superlateral growth regime for 90-nm-thick a-Ge films at room temperature in air by single-shot ELC.