Aluminum(I) and Gallium(I) Compounds: Syntheses,Structures, and Reactions

By the end of the last century there were already the first indications of the possible existence of Al¹ halides. However, it was only through the pioneering works of W. Klemm, who would have celebrated his 100th birthday on January 6, 1996, that detailed spectroscopic investigations became possible. Since the end of the 1970s the reactivity of AlX and GaX species in solid noble gases has been confirmed by numerous examples. In recent years formally monovalent Al and Ga species have been successfully synthesized on a preparative scale. In addition to the first halides, organometallic compounds with metal–metal bonds have been isolated and investigated with regard to their chemical properties. The fundamental importance of such species has been documented in this journal among others in the form of two highlight articles in which experimental and theoretical aspects have been examined with examples, and parallels and differences with respect to boron chemistry have been illustrated. This review is intended to give an account of the chronological development of this research area over the last few years, but an attempt is also made to categorize the experimental results achieved not only with respect to structure, thermodynamics, and reactivity, but also with the aid of quantum chemical calculations and by comparative considerations.     

Microwave modulated photoluminescence in doped GaAs

Microwave modulated photoluminescence (MMPL) is a spectroscopy wherein a sample is placed in the electric field maximum of a microwave cavity and is simultaneously subjected to continuous optical pumping and chopped microwave electric fields. In this work, MMPL has been performed on GaAs epilayers with n- and p-type doping ranging from 10¹⁵ to 10²⁰ cm^-3. The MMPL spectra can be experimentally separated into two categories, fast and slow. The interaction is predominately faster in the lightly doped samples and slower in the heavily doped samples. These observations are consistent with a more-or-less constant rate of lattice heating per free carrier through free carrier energy relaxation. The magnitude of the temperature modulation through free carrier thermalization with the lattice, and hence the amplitude of the slower component of the MMPL, can be explained in terms of theoretical estimates for the rate of energy loss of the accelerated free carriers.     

镓与锗或硒联用对小鼠S180肉瘤及骨中镓,磷,钙含量的影响

以Ｓ１８０肉瘤细胞移植于昆明小鼠前肢腋窝皮下，随机分为阴性对照组（水组）、镓组、镓锗组及镓硒组。每日胃饲一次，２周后，取出肿瘤称重并设正常对照组，并摘取前肢骨骼，则骨中镓、磷、钙含量、结果提示骨饲人药组、三组瘤重显著低于水组，抑制率分别为６４．４％，５２．６％及５４．９％，骨中镓含量，给药组皆大于正常组及水组，口服镓盐皆能进入骨质。镓锗组骨镓含量低于镓组，可能锗拮抗了镓进入骨，而镓硒组骨镓含量则高     

碳氮膜的研究进展

简要回顾了碳氮膜的发展历史，综述了碳氮膜研究的最新进展，并对这类膜的发展前景进行了展望。     

An improved LCAO SCF method for three-dimensional solids and its application to polyethylene,graphite, diamond,and boron nitride

An improved semi-empirical self-consistent scheme is described for calculating the band structures of three-dimensional solids. The basic level is that of CNDO theory. The non-orthogonality of the Bloch functions is recognised and allowance is made for all degrees of involvement of the overlap matrix. The calculation of the electron-repulsion integrals is formulated in a way suitable for solid-state problems. The method is tested on the standard systems; polyethylene, graphite, diamond, and hexagonal and cubic boron nitride. It is found that the valence band properties are satisfactorily reproduced. For optical spectra a configurational interaction scheme is required.     

Nanoindentation characterization of GaN epilayers on A-plane sapphire substrates

Gallium nitride (GaN) epilayers was deposited on a-axis sapphire substrate by means of metal-organic chemical vapor deposition (MOCVD) method. The GaN epilayers has been investigated in their repetition pressure-induced impairment events from nanoindentation technique and, the relative deformation effect was observed from atomic force microscopy (AFM). From the morphological studies, it is revealed that none of crack and particle was found even after the indentation beyond the critical depth on the residual indentation impression. The ‘pop-in’ event was explained by the interaction of the deformed region, produced by the indenter tip, with the inner threading dislocations in the GaN films. Pop-in events indicate the generation and motion of individual dislocation, which is measured under critical depth and, no residual deformation of the GaN films is observed.     

Minority carrier diffusion lengths in bulkn-type gaas

Minority carrier hole diffusion lengths in as-grown and Ni- or Cu-diffused bulkn-GaAs, both LEC and HB, having carrier concentrations in the range 10¹⁶-10¹⁷cm⁻³ have been studied by surface photovoltage methods and trap concentrations determined by DLTS measurements. Data are available for a wide range of specimens and therefore a method of correlation ofL _p with electron trap concentrations has been developed that allows easy identification of the dominant recombination center. This is determined to be the level at aboutE _c -0.40 eV, termed EL5 in earlier studies of electron traps.     

何以为镓？

Gallium is the 31st element in the periodic table of elements. In this paper, the discovery, nature and application of gallium are introduced in the form of storytelling, aiming at giving readers a full understanding of "what is gallium?"     

X‐Ray Investigations of the intrinsic Carbon‐Incorporation during the MOVPE Growth of AlxGa1‐xAs

We have investigated the intrinsic C‐incorporation during the metalorganic vapour‐phase epitaxy of GaAs, (Al,Ga)As, and AlAs. The carbon from the methyl radicals of trimethylgallium and trimethylaluminium has been used as intrinsic carbon source and the necessary growth conditions (low growth temperatures and low V/III‐ratios) have been determined. Under these conditions we observed a reduction of the Al‐incorporation in (Al,Ga)As resulting from a change of surface kinetics at low temperatures. We have used the tensile tetragonal lattice distortion due to the C‐incorporation for determination of the carbon concentration. This has been done by investigating the symmetric (004) reflection peaks of GaAs and the strained epitaxial layer by high resolution x‐ray diffraction. The resulting carbon concentrations showed a good agreement with the hole concentrations determined by Hall measurements and spectroscopic ellipsometry.     

Gallium nitride emitting devices preparation and properties

GaN:Zn//Al₂O₃ electroluminescent devices have been obtained with a wide range of emitted colours (blue, green, yellow and red) ; theses devices have high potential since external quantum efficiencies greater than 1 % and power efficiencies of about 10⁻³ have been reported. On the other hand, from the literature it seems that each colour is obtained randomly, since apparently the same method of preparation is used. We show that the properties of GaN:Zn (conductivity type, cathodoluminescence (peaks and efficiency)) can not be related uniquely to the partial pressure of zinc during the growth, but it is also necessary to take into account the partial pressure of HCl and the thickness of the π layer in order to obtain a satisfactory representation of these properties. From this knowledge, one can deduce the different parameters for growing layers for devices and control their properties. The device fabrication consists of the deposition of a Zn doped thin layer, which is nearly insulating but with p tendency (π layer), onto a Zn doped n type layer. It is demonstrated that the characteristics of the devices (I(V) curves, electroluminescent peaks and efficiencies are related to the characteristics of the π layer and on the transition from n to π. Blue LEDS with characteristics very similar to p-n junction characteristics have been obtained. This work has been supported by DGRST (Délégation a la Recherche Scientifique et Technique).