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The effect of the heterojunction interface on the performance of high bandgap InxGa1−xP:Te/Al0.6Ga0.4As:C tunnel junctions (TJs) was investigated. The insertion of 30 Å of GaAs:Te at the junction interface resulted in a peak current of 1000 A/cm2 and a voltage drop of ∼3 mV for 30 A/cm2 (2000× concentration). The presence of this GaAs interfacial layer also improved the uniformity across the wafer. Modeling results are consistent with experimental data and were used to explain the observed enhancement in TJ performance. This architecture could be used within multijunction solar cells to extend the range of usable solar concentration with minimal voltage drop.

We demonstrate a light-emitting diode (LED) structure with multiple quantum wells (MQWs) conformally grown on semipolar and nonpolar plane facets of n-GaN nanowires (NWs), followed by deposition of fully coalesced p-GaN on these nanowires. Overgrowth on the nanowires’ tips results in inclusion of high density voids, about one micron in height, in the GaN film. The light output intensity of NWs LEDs is more than three times higher than corresponding c-plane LEDs grown simultaneously. We believe this results from a reduced defect density, increased effective area of conformally grown MQWs, absence of polar plane orientation, and improved light extraction.

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I t , is shown that the coloured reaction product of zirconyl ions and alizarin sulphonate is of definite compositioii and stable in acid solution. The reaction is almost specific for zirconium and can be used for its determination in magnesium alloys, iron and steel, and. minerals. A rapid method for determining the approximate composition of hafniumzirconium salt mixtures is also indicated.The method compares favourably in accuracy, speed and cost with the standard gravimetric procedure.THE determination of zirconium in magnesium alloys assumed major importance when the remarkable mechanical properties of these alloys was realised. They are to-day one of the major groups of magnesium-base alloys widely used in aircraft construction. The composition generally varies within fairly narrow limits, and the alloys may contain up to 5 per cent. of zinc, 3 per cent. of rare earths (of the Mischmetall type), and not more than about 1 per cent. of zirconium. A small proportion of the alloys contains thorium. The zirconium is present to a large extent in solid solution, 1 per cent. representing its solid solubility. A small fraction of the zirconium is present as internietallic compounds with iron, manganese, aluminium and silicon; these are insoluble in magnesium and only sparingly soluble in mineral acids, but are soluble in hydrofluoric acid. In general, the insoluble portion is of little interest and, for the purpose of analysis, the only account ta.ken of it is in specifying the concentration and amount of acid used for solution.The method of analysis laid down in D.T.D. specifications involves solution in acid, separation of zirconium with ammonium hydroxide, separation from rare earths by hydrolysis with hexamine, precipitation of zirconium arsenate and ignition, removing arsenic by treatment with sugar charcoal during a further ignition and weighing as the oxide. Although accuracy can belattained by this procedure it is tedious, lengthy and expensive; silica crucibles used for the determination rarely outlast four ignitions without seriously flaking. Furthermore, the conversion factor is rather large (0.7403).The same criticisms apply to the many organic precipitants of the arsonic acid type. Precipitation as phosphate necessitates preliminamy separations, and the ignited precipitate Sept., 19521 OF ZIRCONIUM BY MEANS OF ALIZARIN-S 477of pyrophosphate is frequently grey in spite of prolonged ignition, and sometimes contains slightly less zirconium than would correspond to ZrP,O,.A great deal of literature has appeared recently recommending various organic precipitants for separating zirconium from rare earths and thorium; these include mandelic acid,l@-chloro-and fi-bromo-mandelic acid and other glycollic acid derivatives,,~~ phthalic acid,4 sodium flavianate? m-cresoxyacetic acid,6 hydrazine sulphate,' t a n ~~i n , ~J aneurine and adenylpyrophosphoric acid, lO and cupferron.11 With the exception of fi-bromo-mandelic acid all these reagents finally yield the oxide, so that comparatively large weights of sample a...