Abstract. The observation of neutrinoless double-beta decay (0νββ) would show that lepton number is violated, reveal that neutrinos are Majorana particles, and provide information on neutrino mass. A discovery-capable experiment covering the inverted ordering region, with effective Majorana neutrino masses of 15 − 50 meV, will require a tonne-scale experiment with excellent energy resolution and extremely low backgrounds, at the level of ∼0.1 count /(FWHM·t·yr) in the region of the signal. The current generation 76 Ge experiments GERDA and the Majorana Demonstrator, utilizing high purity Germanium detectors with an intrinsic energy resolution of 0.12%, have achieved the lowest backgrounds by over an order of magnitude in the 0νββ signal region of all 0νββ experiments. Building on this success, the LEGEND collaboration has been formed to pursue a tonne-scale 76 Ge experiment. The collaboration aims to develop a phased 0νββ experimental program with discovery potential at a half-life approaching or at 10 28 years, using existing resources as appropriate to expedite physics results.

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Extremely early phases of the catastrophic optical damage (COD) process in 808-nm emitting GaAs/Al 0 .35 Ga 0 .65 As high-power diode lasers are prepared by the application of short single current pulses. Typical energy entries during these pulses are on the order of 100 nJ within several 100 ns. The resulting defect pattern is investigated by high-resolution microscopy. The root of the COD is found to be located at the waveguide of the laser structure. Analysis of material composition modifications as a result of early COD phase points to melting being involved in the process. During recrystallization, an Al-rich pattern is formed that encloses a volume of a few cube micron of severely damaged material.

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The local vibrational mode absorption lines at 3079.2 and 983.3 cm -1 , measured in semi-insulating LECgrown GaAs, are due to the stretching and wagging mode of one hydrogen bonded to a light impurity atom. The investigation of GaAs grown without boric oxide encapsulant delivers arguments that this impurity atom is nitrogen in the nitrogen-vacancy (N As -V Ga ) defect, which is responsible for the vibrational quadruplet line at 638 cm -1 .