(oral talk) Effect of rapid thermal annealing on optical and structural properties of fs-laser surface processed Ge

Germanium (Ge) is an efficient semiconductor for near-infrared (NIR) detection due to its narrow band gap, high absorption coefficient, compatibility with silicon manufacturing technologies, etc. To avoid reflection of near IR rays from the Ge crystal planar surface and to increase its absorption coefficients at below-bandgap wavelengths, the techniques of surface processing with a femtosecond (fs) laser have recently been developed. Laser treatment generally produces a disordered surface layer which can be reconstructed by rapid thermal annealing (RTA) to eliminate crystal lattice defects and restore the crystalline structure. In this work, the technique of fs-laser processing followed by RTA was applied to the n-type single-crystal Ge wafer precoated with a 50 nm Ti film as a dopant precursor. The results of absorption measurements and Raman spectra of the fabricated Ge samples after RTA treatments with different temperatures are analyzed. The optimized RTA process made it possible to reach the acceptable optical parameters of the processed samples. In conclusion, the techniques of fs-laser texturing followed by RTA have been successfully developed on Ti-coated Ge, aiming to enhance the performance of Ge-based IR detectors.