Time resolved spectroscopy of Ge-H stretching vibrations in hydrogenated amorphous germanium

Transient grating and photon echo measurements of Ge-H stretch modes in hydrogenated amorphous germanium are reported. These experiments reveal that the Ge-H vibrational population decays into two bending modes at 570 cm−1, with the excess energy bridged by Ge-Ge vibrations of the amorphous host. The vibrational dephasing has an excitation density dependence (as has been observed for Si-H stretch modes in amorphous silicon) which we attribute to additional dephasing contributions from non-equilibrium phonons. At temperatures above 30 K, the dephasing rate follows an exponentially activated trend due to elastic phonon scattering processes.