6 research outputs found
Atom probe tomography characterisation of a laser diode structure grown by molecular beam epitaxy
Atom probe tomography (APT) has been used to achieve three-dimensional characterization
of a III-nitride laser diode (LD) structure grown by molecular beam epitaxy (MBE). Four
APT data sets have been obtained, with fields of view up to 400 nm in depth and 120 nm in
diameter. These data sets contain material from the InGaN quantum well (QW) active
region, as well as the surrounding p- and n-doped waveguide and cladding layers, enabling
comprehensive study of the structure and composition of the LD structure. Two regions of
the same sample, with different average indium contents (18% and 16%) in the QW region,
were studied. The APT data are shown to provide easy access to the p-type dopant levels, and the composition of a thin AlGaN barrier layer. Next, the distribution of indium within
the InGaN QW was analyzed, to assess any possible inhomogeneity of the distribution of
indium (“indium clustering”). No evidence for a statistically significant deviation from a
random distribution was found, indicating that these MBE-grown InGaN QWs do not require
indium clusters for carrier localization. However, the APT data show steps in the QW
interfaces, leading to well-width fluctuations, which may act to localize carriers.
Additionally, the unexpected presence of a small amount (x = 0.005) of indium in a layer
grown intentionally as GaN was revealed. Finally, the same statistical method applied to the
QW was used to show that the indium distribution within a thick InGaN waveguide layer in
the n-doped region did not show any deviation from randomness
Broadband sensitization of 1.53 mu m Er3+ luminescence in erbium-implanted alumina
Experimental evidence of an efficient broadband sensitization mechanism in erbium-implanted alumina is presented. Alumina thin films were deposited by plasma-enhanced chemical vapor deposition using trimethyl-amine alane and nitrous oxide. The as-grown films, together with sapphire crystals, were implanted with erbium. Photoluminescence excitation spectra showed that erbium-implanted sapphire crystals exhibit characteristic Er3+ luminescence at 1.53 mum only when pumped resonantly. In contrast, erbium-implanted alumina thin films exhibit 1.53 mum luminescence even when pumped at wavelengths outside Er3+ absorption bands. We postulate that the sensitizing species is either small nanoclusters of aluminum or pairs of aluminum ions. (C) 2004 American Institute of Physics