Stability of Pseudomorphic and Compressively Strained Ge 1-X Sn x Thin Films under Rapid Thermal Annealing

Thin film Ge 1-x Sn x with Sn mole fractions up to 7 % were grown using chemical vapor deposition on Si substrates with a relaxed Ge buffer. Rapid thermal annealing at 550 to 700 °C resulted in film relaxation and Sn segregation. X-ray diffraction rocking curves and reciprocal space mapping of the films showed a reduction in strain after annealing. Samples with Sn mole fractions of 3.2, 6.0, and 7.0 % were partially relaxed when annealed above 550 °C for 30 seconds. Raman spectroscopy of the Ge-Ge longitudinal optical phonon showed a red shift for samples with Sn mole fraction ≤ 6 %, which indicates an increase in Sn atom incorporation within the lattice due to annealing. Photoluminescence measurements of CMOS compatible annealing below 450 °C showed an initial reduction in film quality for short time annealing, but an increase in photoluminescence intensity was observed for longer annealing time.