Ga Sb Research Articles

Co-doping carbon tetrabromide (CBr 4) and antimony (Sb) on GaAs [1 0 0] in solid source molecular beam epitaxy

The surfactant effects of antimony enhances the carbon (C) dopant incorporation into substitutional sites in GaAsSb:C grown by solid source molecular beam epitaxy. A hole mobility greater than 50 cm 2/V s for doping levels over 9×10 19 cm −3 was achieved using a solid CBr 4 source. 5.4×10 −8 Torr of carbon flux giving a hole concentration of ∼7×10 19 cm −3 in GaAs, reaches beyond 9×10 19 cm −3 with the addition of ∼4×10 −8 Torr of Sb. With increasing Sb doping concentration, the rate of C incorporation into substitutional sites increases, the photoluminescence characteristics are improved and the net hole concentration increases due to the reduction of interstitial carbon. However when Sb doping is increased further, gallium vacancies and Ga Sb antisites could create point defects, causing epitaxial degradation.

Phase equilibria in the quasibinary GaSb?Pb system

The phase relationships of the quasibinary GaSb–Pb section of the ternary Ga–Sb–Pb system were studied by means of the X-ray diffraction (XRD) and optical microscopy. Phase reactions were determined using differential thermal analysis (DTA). Based on this results phase diagram of the GaSb–Pb section was constructed, which was compared with literature data.

Obtaining GaSb/InAs heterostructures by liquid phase epitaxy

Features of liquid phase epitaxy of GaSb/InAs heterostructures are considered. A modified method of pulse cooling of saturated solution-melt is offered. This method allows us to avoid InAs substrate dissolution during contact with a Ga–Sb liquid phase. Also it is shown that forming InxGa1−xAsySb1−y solid solutions due to GaSb epitaxial layer dissolution by InAs substrate is energetically unfavourable.

Materials growth for InAs high electron mobility transistors and circuits

High electron mobility transistors (HEMTs) with InAs channels and antimonide barriers were grown by molecular beam epitaxy. Both Si and Te were successfully employed as n-type dopants. Sheet resistances of 90–150 Ω/□ were routinely achieved on a variety of heterostructures with nonuniformities as low as 1.5% across a 75 mm wafer. X-ray diffraction measurements show that the InAs channels are in tension, coherently strained to the Al(Ga)Sb buffer layers. Atomic force microscopy measurements demonstrate that the surfaces are relatively smooth, with rms roughness of 8–26 Å over a 5×5 μm2 area. These results demonstrate that the growth of InAs HEMTs has progressed to the point that the fabrication of circuits should be feasible.

Prediction of the thermodynamic properties for the Ga–Sb–Pb ternary system

The results of some thermodynamic prediction methods applied to the Ga–Sb–Pb ternary system are presented in this paper. The Chou general solution model and the traditional models of Kohler and Toop were included in the calculation for the comparison and discussion. Integral enthalpy of mixing and integral excess Gibbs energy dependences on composition for the 15 investigated cross sections at 973 K and 1073 K, respectively, were obtained according to the applied models. The comparison between the results of the three models shows good mutual agreement. Obtained results were used for the further calculation of partial molar quantities for every component of the investigated ternary system. Calculated activity values at 1073 K for all components are given in the form of isoactivity diagrams.

Growth mechanism in heavily carbon-doped GaAs xSb 1− x grown by MOCVD

The InP/GaAsSb material system has type-II band structures and can provide ideal band structures for HBT operation. For the fabrication of HBTs, the growth of p-GaAsSb, which is used as a base layer in HBT structures, must be clarified. We investigated the change of GaAsSb growth behavior that occurs by adding CBr 4 as a p-type dopant gas. As the CBr 4 partial pressure in the vapor phase increased, the growth rate and Sb composition of the GaAsSb layer decreased. The CBr 4 partial pressure dependence of growth rate is well interpreted by the formula derived from two chemical equilibrium equations: one the pyrolysis static reaction of CBr 4, and the other the etching static reaction between HBr and Ga. From the fitting formula, GaSb in GaAsSb is found to be etched three times faster than GaAs in GaAsSb, resulting in a decrease of Sb composition in the GaAsSb solid phase with an increase of CBr 4 partial pressure. Additionally, the growth rate of C-doped GaAsSb is found to be independent of the V/III ratio, although Sb composition in the solid phase monotonically decreased with increasing V/III ratio.

Lanthanum gallium bismuthide, LaGaBi2.

The ternary rare-earth gallium bismuthide LaGaBi(2) has been prepared through reaction of the elements. Its structure (Pearson symbol hP24, hexagonal, space group P6/mmm, Z = 6, a = 13.5483(4) A, c = 4.3937(1) A) contains columns of La(6) trigonal prisms centered by Bi atoms. These columns are surrounded by a framework consisting of three-atom-wide Bi ribbons and Ga(6) rings. Additional Bi atoms are sandwiched between pairs of Ga(6) rings. LaGaBi(2) is structurally closely related to La(13)Ga(8)Sb(21). A retrotheoretical analysis of the structure through extended Hückel band structure calculations suggests an interesting electronic situation in which strong multiple bonding in the Ga-Ga network coexists with weak hypervalent bonding in the Bi-Bi network and confirms the metallic behavior seen in electrical resistivity measurements.

Atomic Ordering in Self-assembled Epitaxial and Endotaxial Compound and Element Semiconductor Quantum Dot Structures: The First Review

AbstractAlthough the main international research thrust on self-assembled epitaxial semiconductor quantum dots is currently being directed towards random alloy quantum dots, the suggestion is made that atomically ordered quantum dots which are grown by either epitaxy or endotaxy may in addition to their larger quantum confinement potentials possess superior long term structural stability. Such atomically ordered quantum dots should, therefore, be superior to random alloy quantum dots as far as prospective device applications are concerned. The basis for this suggestion is simple thermodynamic considerations. These considerations seem to explain our transmission electron microscopical observations of epitaxially grown atomically ordered In(Sb,As), (In,Ga)Sb, (Cd,Zn)Se, (Cd,Mn,Zn)Se quantum dots and Pb(Se,Te) quantum dot predecessor islands. Atomic ordering in (In,Ga)P quantum dot structures, as recently observed by other authors, does not seem to contradict our thermodynamic considerations. Endotaxially grown atomically ordered (In,Si,As) and (Sn,Si) quantum dots in Si matrices are briefly discussed as an even more unconventional approach to nanostructures with applications in electronics, photonics, information storage, and sensing.

Effect of Growth Interruption on the Properties of GaInAsSb/AlGaAsSb/GaSb Heterostructures and the Performance of Thermophotovoltaic Devices

AbstractThe effect of growth interruption on the properties of GaInAsSb/(Al)Ga(As)Sb heterostructures and on the performance of GaInAsSb/AlGaAsSb/GaSb thermophotovoltaic (TPV) devices grown by organometallic vapor phase epitaxy is reported. In-situ reflectance monitoring is shown to be sensitive for observation of surface degradation during growth interruption, and this data was correlated with materials characterization by high-resolution x-ray diffraction and 4K photoluminescence (PL). Minority-carrier lifetime by time-resolved PL was used to determine interfacial recombination velocity of GaInAsSb/AlGaAsSb and GaInAsSb/GaSb double heterostructures grown with and without interruption, respectively. GaInAsSb/AlGaAsSb TPV devices grown without growth interruption have a slightly higher performance compared to those grown with interruption.

Activity measurement of gallium in the B2 phase of the CoGa–Sb system by the EMF method with zirconia-based solid electrolyte

Gallium activity in the B2 phase regions of both binary Co–Ga and ternary Co–Ga–Sb systems was measured by EMF method with stabilized zirconia solid electrolyte The temperature range was 1073–1273 K and Sb concentrations were 1, 2 and 3 mol fractions. Ga activity at 1173 and 1273 K increases sharply in Ga rich region and the addition of Sb to the CoGa phase increases Ga activity. Activity change corresponds to the lattice parameter change with Sb addition to the CoGa phase.

Composition Conversion Mechanism of InSb into InGaSb

The composition conversion mechanism of InSb into InGaSb when an In–Ga–Sb solution was in contact with an InSb substrate was investigated. Striations were formed in the conversion region by passing electric current pulses. This indicated that the solid and the liquid coexisted during the conversion process. After removing the solution from the substrate, the Ga profiles became smoother and deeper with the increase of annealing period and with the decrease of cooling rate. This proved that the Ga could move down into the InSb substrate during these processes. By the direct observation of the movement of the conversion region on an InSb substrate using a high-temperature optical microscope, the appearance of the {111} facet at the moving front of the region was confirmed. The gradual dissolution of InSb led to the formation of In–Ga–Sb solution belt in the substrate and the subsequent crystallization of InGaSb.

Solid State Phase Equilibria in the Fe—Ga—Sb Ternary System at 600 °C.

Abstract Solid state phase equilibria in the ternary Fe–Ga–Sb diagram were determined at 600 °C using experimental techniques such as X-ray diffraction, electron probe microanalysis and scanning electron microscopy. Very limited solid solutions were measured in the binary constituent Fe–Ga and Fe–Sb compounds except for the e-phase (Fe ≈2.55 Sb 2 ) which extends from 42 to 48 at.% Sb. In the Fe-rich part of the diagram, a ternary phase Fe t Ga 2− x Sb x (2.15≤ t ≤2.80) was evidenced which corresponds in fact to a solid solution into which Ga and Sb substitute one another on the same hexagonal sublattice. This phase, which can be truly considered as a pseudo-binary one since its origin results from the e-phase, shows an extended homogeneity range with a Ga-rich limit corresponding to the formula Fe t Ga 0.8 Sb 1.2 . Moreover, it crystallizes in hexagonal symmetry with a disordered structure derivative from the NiAs-type ( B 8 1 ). This pseudo-binary phase is in thermodynamic equilibrium with all the binaries of the system except FeGa 3 . The main result of the ternary Fe–Ga–Sb diagram remains the existence of a diphasic region between the Fe t Ga 2− x Sb x phase (1.2≤ x ≤1.6; 2.15≤ t ≤2.80) and the semiconductor GaSb. Nevertheless, at 600 °C, this pseudo-binary phase does not extend up to the Fe 3 GaSb composition which is stoichiometric in Ga and Sb. Finally, a comparative study has been made with the three other ternary systems Fe–Ga–As, Ni–Ga–As and Ni–Ga–Sb previously reported, and the consequences for the solid state interdiffusions in Metal/III–V semiconductor heterostructures are discussed.

The structures, electronic states and properties in liquid Ga–Sb and In–Sb systems

The atomic structures of liquid GaSb and InSb and the electronic structures of liquid GaSb have been studied with the extended X-ray absorption fine structure and the X-ray absorption near edge structure techniques, respectively. The results demonstrate that the melting of GaSb and InSb destroys most of the covalent network. The local atomic arrangement and the density of state around the Fermi level in these liquids exhibit a metallic behavior. However there still exist some covalent bonds in the liquids showing slight features of the crystalline state. The temperature and composition dependence of the electrical properties in liquid Ga 1− x Sb x and In 1− x Sb x (0⩽ x⩽1) were systematically studied with a high measurement accuracy. Some anomalous behavior of the electrical properties in certain compositions was observed. The special character of electronic transport may be due to further structural changes in the liquids at temperatures above their melting points.

The hidden structure in liquid IIIB–VB alloys

The electrical resistivity, ρ, of liquid Ga–Sb and In–Sb alloys was measured by the dc four probe technique. The value of ρ remains metallic in character and the simple parabolic shape of the Nordheim rule is observed, in spite of the existence of intermetallic compounds with semiconductor properties at the 1:1 composition. However, the concentration dependence of the temperature dependence of ρ, d ρ/d T, for these systems shows a minimum respectively at the eutectic compositions, which are present in the Sb-rich range for both systems. In the extreme case of Ga–Sb alloys d ρ/d T is negative near the eutectic composition and the eutectic temperature, though ρ itself shows a metallic value of an order of 100 μΩ cm. The existence of an anomaly only in d ρ/d T implies that some hidden structure is present near the eutectic point in the respective liquid state. The anomalous behavior of ρ was successfully explained by the existence of concentration fluctuations, based on the effective medium theory, for which three kinds of domains exist. These are the domains of the semiconductor-like GaSb intermetallic compound, of the metallic-like Sb and of the metallic homogeneous liquid.

High-resolution patterning of semiconductors using electron-beam-assisted wet etching

Chemical wet etching as a lithographic technique often suffers from strong underetching underneath the mask, limiting the achievable size of the structures. We have developed a chemical wet etching technique in which the etching rate and anisotropy of the process is controlled by electron-beam exposure, resulting in structures with lateral dimensions down to 12 nm. Results are shown for (Al,Ga)Sb–InAs quantum-well structures and InAs layers. A possible mechanism is discussed.

Solid state phase equilibria in the Fe–Ga–Sb ternary system at 600 °C

Solid state phase equilibria in the ternary Fe–Ga–Sb diagram were determined at 600 °C using experimental techniques such as X-ray diffraction, electron probe microanalysis and scanning electron microscopy. Very limited solid solutions were measured in the binary constituent Fe–Ga and Fe–Sb compounds except for the ε-phase (Fe ≈2.55Sb 2) which extends from 42 to 48 at.% Sb. In the Fe-rich part of the diagram, a ternary phase Fe t Ga 2− x Sb x (2.15≤ t≤2.80) was evidenced which corresponds in fact to a solid solution into which Ga and Sb substitute one another on the same hexagonal sublattice. This phase, which can be truly considered as a pseudo-binary one since its origin results from the ε-phase, shows an extended homogeneity range with a Ga-rich limit corresponding to the formula Fe t Ga 0.8Sb 1.2. Moreover, it crystallizes in hexagonal symmetry with a disordered structure derivative from the NiAs-type ( B8 1). This pseudo-binary phase is in thermodynamic equilibrium with all the binaries of the system except FeGa 3. The main result of the ternary Fe–Ga–Sb diagram remains the existence of a diphasic region between the Fe t Ga 2− x Sb x phase (1.2≤ x≤1.6; 2.15≤ t≤2.80) and the semiconductor GaSb. Nevertheless, at 600 °C, this pseudo-binary phase does not extend up to the Fe 3GaSb composition which is stoichiometric in Ga and Sb. Finally, a comparative study has been made with the three other ternary systems Fe–Ga–As, Ni–Ga–As and Ni–Ga–Sb previously reported, and the consequences for the solid state interdiffusions in Metal/III–V semiconductor heterostructures are discussed.

Numerical simulation of effect of ampoule rotation for the growth of InGaSb by rotational Bridgman method

To investigate the solution convection for the rotational Bridgman method, both flow patterns and temperature distributions in the In–Ga–Sb solution were calculated. In the three-dimensional model, In–Ga–Sb solution was put between a GaSb seed and feed crystals, where the seed and feed crystals were of cylindrical shape, and the In–Ga–Sb solution was of semi-cylindrical shape. The flow velocity in the In–Ga–Sb solution increased and the temperature distribution tended to be uniform with increase of the ampoule rotation rate. When the ampoule rotation rate was 0 rpm, the temperature difference at the solid–liquid interface increased with an increase of the aspect ratio. However, with an increase of ampoule rotation rate, the temperature difference became small. The stirring effect of the ampoule rotation was enhanced with an increase of rotation rate as the forced convection became dominant in the In–Ga–Sb solution.

The Structure of Oxide Ga–Sb–Ni–P–W–O/SiO2 Catalyst and Its Catalytic Properties in Propane Ammoxidation

The structure of the multicomponent catalyst Ga1Ni1P2W0.5Sb6Ox /SiO2 and its catalytic properties in propane ammoxidation are studied. The catalyst is nanostructured and consists of noncoherently spliced blocks of a multiply promoted phase with a structure of gallium antimonate, which covers SiO2 particles with a thin layer. In the multiply promoted compound with a structure of gallium antimonate, Ni2+ ions partially substitute for Ga3+ and W6+ ions partially substitute for Sb5+. This leads to an increase in the crystalline lattice parameters a and c. Phosphate ions are stabilized in the region of block interfaces. The catalyst is characterized by high efficiency in propane ammoxidation.

Room-temperature ferromagnetism in zincblende CrSb grown by molecular-beam epitaxy

Thin films of CrSb grown by solid-source molecular-beam epitaxy on GaAs, (Al, Ga)Sb, and GaSb are found to exhibit ferromagnetism. Reflection high-energy electron diffraction and high-resolution cross sectional transmission electron microscopy both indicate that the structure is zincblende. Temperature dependence of remanent magnetization shows that the ferromagnetic transition temperature is beyond 400 K.

Internal self-ordering in In(Sb,As), (In,Ga)Sb, and (Cd,Zn,Mn)Se nano-agglomerates/quantum dots

Nano-agglomerates of In(Sb,As) in InAs, (In,Ga)Sb in GaSb, and (Cd,Zn,Mn)Se in (Zn,Mn)Se are classified by transmission electron microscopy. In scanning transmission electron microscopy, atomic resolution Z-contrast images reveal different modes of internal compositional modulation on the atomic length scale, resulting for all three material systems in nano-agglomerates of an appropriate size that may constitute a new type of quantum dot. For other nano-agglomerates of In(Sb,As) in InAs and (In,Ga)Sb in GaSb, we observed a second type of nanoscale ordering that results in nano-agglomerates with an internal compositional modulation on a length scale of a few nm. Both types of compositional modulation are discussed as having arisen from a rather long-term structural response to a combination of internal and external strains.