A far-infrared p-type germanium laser with active crystal prepared from ultra pure single-crystal Ge by neutron transmutation doping (NTD) is demonstrated. Calculations show that the high uniformity of Ga acceptor distribution achieved by NTD significantly improves average gain. The negative factor of stronger ionized impurity scattering due to high compensation in NTD Ge is shown to be unremarkable for the gain at moderate doping concentrations sufficient for laser operation. Experimentally, this first NTD laser is found to have lower current-density lasing threshold than the best of a number of melt-doped laser crystals studied for comparison.
A neutron transmutation doped (NTD) far-infrared p-Ge laser crystal and a melt-grown p-Ge laser are analyzed and compared. Though the doping level in the NTD active crystal is twice lower than optimal, the laser performance is comparable to that produced from high-quality melt-grown crystals because of superior dopant uniformity. Compensation was examined by comparing results of neutron activation analysis with majority carrier concentration. Study of impurity breakdown electric field reveals better crystal quality in NTD. The current saturation behavior confirms the expected higher doping uniformity over melt grown laser rods.
Far-infrared p-Ge laser operation in an active crystal prepared by transmutation doping is demonstrated for the first time. Though saturated current density in the prepared active crystal is twice lower than optimal, the laser performance is comparable to that of good lasers made from commercially produced melt grown p-Ge. The current saturation behavior of this material confirms the expected higher doping uniformity over melt grown laser rods.