Free-Carrier Radiation Peak in GaAs Due to Valence-Band Maxima Arising from Terms Linear ink

A new peak has been observed 0.4 meV above the direct band-to-band-transition radiation at 1.5202 eV in the 1.4°K photoluminescence spectrum of high-purity epitaxial GaAs. This new peak is attributed to the recombination of free electrons of nonzero k with free holes in the linear-$k$ valence-band maxima, which are estimated to be ≈3×${10}^5$ ${\mathrm{cm}}^{-1\mathrm{}}$ away from and ≲1×${10}^{-4\mathrm{}}$ eV above the k=0 maximum.