The research results of photoelectric, optical and recombination properties of neutron transmutation doped (NTD) semiconductor solid alloys Si 1-xGe x (x = 0.008-0.112) are presented in spectral range 0.8-10.6 μm. It is shown that these properties of NTD Si 1-xGe x are determined by creation of transmutation impurities of Se and Ga as well as by variation of Ge content and compensation. The theoretical and applied aspects of the NTD Si 1-xGe x have been also considered.