Cathodoluminescent properties of Eu2+‐ or Ce3+‐activated
normalMgS
and
Ca1−xMgxS
phosphors are investigated at 300 K. It is found that
normalMgS:normalEufalse(0.01 normalmole percent false[normalm/normalofalse]false)
exhibits a high energy efficiency (∼16 %) and an improved water‐resistance if residual oxide content is less than 1 m/o. Under these highly sulfurizing conditions,
normalMgS
is confirmed to be completely miscible with
normalCaS
in any compositional ratio. The composition
Ca0.1Mg0.9S:normalEufalse(0.05 normalm/normalofalse)
, Ba(0.1 m/o), whose color coordinates are comparable to the red phosphor
false(Y0.964Eu0.036)2O2S
, exceeds the latter in brightness by 15% at 18 kV excitation. Additionally, Eu2+‐activated alkaline‐earth binary sulfides are examined. A complete miscibility is ascertained in the pseudobinary system where the difference in cation radius is less than 0.035 nm. Stress‐induced peak shifts are observed in
normalMgS:normalEu
and
A1−yBySfalse(AnormalorB≡normalMg,normalCa,normalSr or Ba,A≢Bfalse)
. Some mechanisms for these shifts are proposed.
A new orange-emitting phosphor, (Ca, Mg)S:Mn, was developed to replace a Cd compound, Cd,~,(PO4),~C12:Mn, which is potentially an environmental problem. With 1.5% Mg and 0.8% Mn, the emission color of (Ca, Mg)S:Mn is equal to the brightness ofa 9 or 12 in. monochromatic tube and is 20% higher than that of Cd,,,(PO4)~Cl_
Preparation of single crystal heterojuctions is investigated in the vapor growth of GaAs on Ge or of InAs on GaAs substrate by varying their basic growth parameters such as source and substrate temperatures, iodine carrier concentration and crystal orientation. The relations between growth conditions, growth rate and crystal quality are discussed.
The most remarkable feature is the appearance of an intermediate layer of 10–20 µ thick between substrate and grown film which is observed over a rather wide range of growth conditions and which plays a fairly important role in junction electrical properties.
Experimental results suggested that the origin of this intermediate layer was strongly connected with the species that was once vaporized from the substrate and precipitated in the closed tube.
Electron mobility, minority-carrier lifetime, and misfit-dislocation density are measured along the layer thickness direction near the interfacial regions of GaAs crystals grown on GaAs and Ge substrates by vapor phase epitaxy. It is observed that the mobility and lifetime decrease, while the dislocation density increases exponentially, as the layer thickness is decreased. These phenomena are found to be consistently caused by out-diffusion of interstitial Ga vacancies introduced at the epitaxial layer/substrate interface in the stage prior to growth or in the first stage of growth. The diffusion coefficient of the interstitial Ga vacancy (off-centered Ga atom) is estimated to be 3.6×10−5 exp(−11800/T) cm2/sec based on the experimental results.
Neodymium pentaphosphate (NdP5Oz4) single crystals are grown from polyphosphoric acids by controlling polymerization rate of the acids as a main growth parameter, Solubility of NdP5OI4 in polyphosphoric acids as well as morphology and growth rate of NdP5014 crystals are empirically correlated with polymerization rate, expressed by mean-condensed rate in this study. Based on thedata for epitaxial growth rates along <100>, <010>, and <001> axes, it becomes clear that morphological change of spontaneously nucleated crystals occurs because each axis growth rate shows a different polymerization rate dependence. The influence of temperature gradient given to phosphoric acid is also investigated. As a result, the shape of spontaneously nucleated NdP5Oz4 crystals can be arbitrarily controlled with rather high reproducibility.
Die strukturelle Qualität einer auf Ge epitaktisch gewachsenen GaAs‐Schicht wird als Funktion des Abstandes von der GeAs‐Ge‐Grenzfläche durch Messung der Kathodo‐ und Photolumineszenzeigenschaften bei 77 K und der elektrischen Eigenschaften bei 350 K untersucht (Röntgentopographie, Transmissionselektronenmikroskopie).
Compositionally graded layers of GaAs1−xPx grown on (100) planes of GaAs substrates were investigated as a function of the distance t from the substrate, using a 77 °K cathodoluminescence technique. It was found that luminescence intensity L of these layers was strongly dependent on the profile of the compositional gradient, dx/dt. A number of the nonradiative recombination centers are three−dimensionally distributed in the shape of a cross−grid. This is related to misfit dislocations associated with impurities in the graded layers. The gradient dependence of L demonstrates that the density of these nonradiative recombination centers, N, is proportional to (dx/dt)2. This quadratic relation shows that only grading profiles which satisfy the condition d2x/dt2<0 can successfully decrease N continuously with increasing t. Discontinuous variations of x and/or dx/dt cause a significant degradation in the subsequent layers. From the spatial variation in the ratio of the intensity of the 1.35−eV band to the near−gap band, it was found that an anomalous accumulation of Cu contaminant occurred at the substrate−epitaxial−layer interface region, where a relatively high density (∼4×108 cm−2) of these nonradiative recombination centers was present. This is because of a very steep compositional gradient (∼20% P/μ). Here, the concentration of Cu was optically estimated through cathodoluminescence data from Cu−diffused GaAs samples.
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