Abstract

Ultrafast carrier properties of group-IV semiconductors, such as silicon, germanium, and SiGe superlattices, are topics of growing interest, but these materials remain less studied^1,2 than their III-V cousins because they are indirect semiconductors, for which time-resolved investigations are more difficult. Here we present what we believe to be the first measurements of ultrafast time-resolved photoluminescence from germanium induced by 80-fs pulses from a Ti:sapphire laser with 1.65-eV photons. A time resolution of 100 fs is achieved by using a dispersion-free, high-efficiency upconversion technique. Carrier-accumulation effects due to the high repetition rate of the laser are avoided by using slightly re-doped and neutron-bombarded samples having short carrier lifetimes. All measurements were made at 10 K.

© 1993 Optical Society of America