We investigate the effect of carbon content on the minority carrier lifetime in lattice-matched SiGeC diode structures grown by MBE. A new technique recently proposed by Cerdeira and Estrada ([5], Cerdeira A, Estrada M. Solid-State Electronics 1997;42:727) is used to extract lifetimes in the fabricated samples. The observed nondegradation of lifetime with the addition of carbon is an important result, suggesting the potential usefulness of SiGeC alloys in high speed device applications.