Influence of impurity absorption on germanium hot-hole laser spectra

We investigate the stimulated emission spectra of p-Ge hot-hole lasers. To clarify the influence of impurity absorption we use for the first time a Tl-doped p-Ge laser. Since we observe a clear difference between the spectrum of this laser and that of normally used Ga-doped lasers with respect to the 'emission gap' and to the low-frequency range, we can give definite evidence that impurity transitions are involved in the lasing process.