A study of strain relaxation in GaNxP1−x epilayers grown by chemical beam epitaxy, using a rf-plasma nitrogen radical beam source, tertiarybutylphosphine, and triethylgallium, is reported. Microcracks are observed in GaNxP1−x epilayers grown on GaP when the nitrogen composition is greater than 1.6%. Transmission electron microscopy results show that the tensile-strain relaxation in GaNxP1−x epilayers is initially relieved by microcrack formation without misfit dislocations. These microcracks penetrate through the interface, degrading the crystallinity of the GaP substrate. Microcracks formation can not be alleviated by adjusting the growth rate, growth temperature, V/III ratios, and forward plasma power, but they can be eliminated by reducing the growth area of the GaP substrate.
Hydrazine derivatives are attractive low temperature nitrogen sources for use in MOVPE due to their low thermal stability. However their purification and subsequent analysis has not previously been investigated in depth for this application. A detailed study on 1,1-dimethylhydrazine {(CH 3 ) 2 N-NH 2 } purified by eight different methods and the subsequent quantitative measurements of water present in the samples obtained is reported here. A correlation between 1 H nuclear magnetic resonance spectroscopy (NMR), gas chromatography-atomic emission detection (GC-AED) and cryogenic mass spectroscopy (Cryogenic-MS) has been performed. All three analysis techniques can be used to measure water in the samples and with the best purification the water content can be lowered well below 100 ppm. The high purity of this material has been demonstrated by growth results and the state-of-the-art performance of laser diodes.
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