GaN heteroepitaxial layers grown on spinel substrates have been investigated by the Kossel effect technique. The excitation of GaK, X-rays inside the crystal lattice was carried out either by means of 1.25 MeV protons or 40 KeV electrons. Both methods give similar results concerning the values of the lattice parameters and the sign of polarity.Following the proton irradiation a lattice expansion normal to the surface occurs. A coinparison of our results with those of other authors shows that the growth direction is the same for (1 1 1) spinel skid (0001) sapphire substrates.GaN-Heteroepitaxieschichten auf Spinellsubstrat wurde mittels des Kosseleffektes untersucht. Die Anregung der GaKG-R6ntgenstrahlung im Kristallgitter erfolgte sowohl mit Protonen der Energie 1.25 MeV als auch mit 40 KeV Elektronen. Beide Methoden lieferten ubereinstimmende Ergebnisse hinsichtlich der Gitterkonstanten und der Polarit a t der Epitaxieschicht. Infolge des Protonenbeschusses trat eine Gitterexpansion senkrecht zur Kristalloberfliiche auf. Weiterhin konnte festgestellt werden, daB als Wachstumsrichtung fur (111) Spinellsubstrate die polare [OOOl] A Richtung auftritt, wie es fruher schon von anderen Autoren fur (0001) Korundsubstrate gezeigt wurde.
IT is a commonplace that British government in Uganda was, from its inception, essentially one of benevolent paternalism—just rule by kindly parents. It is also evident that, particularly in the final decade before independence, the dilemma of this policy lay in its conflict with a growing realization that the children would soon come of age. The political aspects of this dilemma are familiar. Its social and economic implications are perhaps less clear.
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