Infrared spectral hole burning of sulfur-hydrogen deep donors in a Si: Ge crystal

Spectral holes which persist for ∼5 msec have been produced in the spectrum of a sulfur-hydrogen complex in a Si-0.1 at.% Ge alloy crystal maintained at 1.7 K. Measurements which combine an infrared laser pump with a Fourier-transform spectrometer probe show that the hole burning is due to migration of electrons from the S-H centers to shallow traps. The large observed hole width (4.6 ${\mathrm{cm}}^{-1\mathrm{}}$) is attributed to spectral diffusion by resonant excitation transfer. The lack of temperature dependence of the hole burning of the $2p_{\pm }$ line below 30 K suggests that excitation transfer is also responsible for the ionization of laser-excited centers in the hole-burning process.