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The luminescence of aluminium nitride, activated by manganese, is described. A structure with equidistant peaks, clearly resolved at low temperatures, is found in the emission band 580 to 620 nm. This structure is interpreted in terms of phonons using the Pekar theory. The energy of the phonon involved is 0.023 eV. The luminescence decay is exponential with a time constant τ = 1.0 × 10−3 s over a wide temperature range. It is suggested that the luminescence is due to transitions between metastable and basic levels of the tetravalent manganese ion.

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Die vorliegende Arbeit behandelt die Züchtung von Aluminiumnitrid‐Einkristallen durch Reaktion aus der Gasphase im Temperaturgebiet von 1750 bis 2050 °C. Es wurde gefunden, daß bei höheren Übersättigungen meist prismatische, bei niedrigeren dagegen plättchenförmige Kristalle entstehen. Zwei Reaktionen die bei dem Wachstum aus der Gasphase zur Geltung kommen können, werden diskutiert. Der Habitus der Kristalle kann dadurch beeinflußt werden, daß die eine oder die andere der beiden angeführten Reaktionen die entscheidende Rolle spielt. Gleichzeitig muß auch die Einwirkung von Verunreinigungen berücksichtigt werden.

Impurity avalanche breakdown in n-type GaAs layers prepared by t h e LPE, VPE and MBE methods has been studied in detail using voltage-controlled current-voltage (1-V) characteristics and luminescence measurements together with computer simulations. Scholl's model of the first-order non-equilibrium phase transition in a two-level system was found to be adequate to describe the main experimental results. The threshold voltage for breakdown depends on the initial free-electron concentration. The hysteresis width diminishes with decreasing binding energy of electrons in the excited states of donors. The changes in luminescence spectra observed during impurity breakdown reflect changes in the charge state of shallow impurities. The band corresponding to B A transitions disappears together with t h e decrease of the exciton radiative recombination rate.In the post-breakdown part of t h e I-V characteristics another region 01 nonlinear behaviour with hysteresis and sharp increase of instabilities was observed. Its origin has not yet been determined unambiguously.

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