ABSTRACT
To analyze the local structure and/or chemical states of boron atoms in boron-doped diamond, which can be synthesized by the microwave plasma-assisted chemical vapor deposition method (CVD-B-diamond) and the temperature gradient method at high pressure and high temperature (HPT-B-diamond), we measured the soft X-ray emission spectra in the CK and BK regions of B-diamonds using synchrotron radiation at the Advanced Light Source (ALS). X-ray spectral analyses using the fingerprint method and molecular orbital calculations confirm that boron atoms in CVD-B-diamond substitute for carbon atoms in the diamond lattice to form covalent B-C bonds, while boron atoms in HPT-B-diamond react with the impurity nitrogen atoms to form hexagonal boron nitride. This suggests that the high purity diamond without nitrogen impurities is necessary to synthesize p-type B-diamond semiconductors.
ABSTRACT
We have studied the cathodoluminescence of AlxGa1-xAs/GaAs multilayers grown on ridge-type triangles by molecular beam epitaxy. The compositional variation of Al, as well as the distribution of impurity and/or defect, was revealed by variations in the cathodoluminescence spectra and images. The Al composition in an AlxGa1-xAs layer was highest in the (111)A facet and decreased in the order (100), (411)A, (111)-delta and (110) facets. On the other hand, the carbon concentration was highest in the (411)A facet and decreased in the order (111)A, (111)-delta, (100) and (110) facets. It should be noted that the (111)-delta facet has a significant effect on the redistribution of Al. Although our ridge-type triangles are rather large for the quantum structures, these data have elucidated the self-organization mechanism of the AlxGa1-xAs/GaAs system and have yielded information on the design of quantum structures. We conclude that cathodoluminescence observation is a powerful tool for studying the compositional variation or band structure of three-dimensional microscale or nanoscale construction.
