Near band-edge optical properties of cubic GaN with and without carbon doping
We report the results of studying the optical properties of cubic GaN thin films with photoluminescence and photoluminescence excitation spectroscopies. The films are deposited by plasma-assisted molecular beam epitaxy on GaAs (001) substrates, with and without intentional doping with carbon atoms (p-type doping). The evolution of the optical spectra of the C-doped samples is consistent with a picture in which carbon enters into N-vacancies at low concentrations, producing a marked improvement in the crystalline properties of the material. At higher concentrations it begins to form complexes, possibly due to interstitial occupation. The temperature dependence on the absorption edge of the doped material is also measured and is analyzed with standard theoretical models.
Near band-edge optical properties of cubic GaN
We used photoluminescence, photoluminescence excitation spectroscopy (PLE) and photoreflectance (PR) to study the optical properties of thin films of cubic GaN, deposited by plasma-assisted molecular beam epitaxy on a GaAs (001) substrate. Our results show a clear step-like absorption edge, resulting from the merging of the free exciton with the continuum. Quantitative values for the absorption-edge energy and lifetime broadening are obtained. The dependence of the latter on temperature, as well as some features of the PR spectrum, reveal that the cubic material still presents residual strain and distortions. A secondary absorption-edge due to hexagonal inclusions is also observed in the PLE spectra.
[Electron microscopic cytochemistry of pseudo-Chediak-Higashi granules in 5 cases of AML].
Blasts from 5 cases of AML with pseudo-Chediak-Higashi granules were examined ultrastructurally and histocytochemically using peroxidase, acid phosphatase, high iron diamine (HID) and periodic acid-thiocarbohydrazide-silver proteinate (PA-TCH-SP) stainings. Pseudo-Chediak-Higashi granules, which appeared as vacuole-like inclusions by light microscopy, generally contained electron-lucent materials. All pseudo-Chediak-Higashi granules were, positive for peroxidase but some were negative for acid phosphatase. Pseudo-Chediak-Higashi granules were HID positive, indicating that they contained sulfated glycoconjugates. Glycogen-like particles were observed in the pseudo-Chediak-Higashi granules with the PA-TCH-SP method, as occasionally observed in granules in drug resistant ALL blasts. In conclusion, the contents of pseudo-Chediak-Higashi granules, which seems to be formed by fusion of small granules, differed from those of normal azurophillic granules.