We have measured the first infrared luminescence spectra of In0.53Ga0.47As with 10‐ps time resolution. From the spectra we have obtained the carrier distribution functions at various delays for two different initial plasma densities. Our results provide a direct measurement of the carrier energy loss rate to the lattice, which we find to be about an order of magnitude slower than predicted from a simple model. We also find that the energy loss rate is surprisingly insensitive to carrier density at high densities.