Zinc Diffusion Research Articles

Zinc diffusion in InAsP/InGaAs heterostructures

A systematic study of the sealed ampoule diffusion of zinc into epitaxially grown InP, In0.53Ga0.47As, In0.70Ga0.30As, In0.82Ga0.18As, and through the InAsP/InGaAs interface is presented. Diffusion depths were measured using cleave-and-stain techniques, electrochemical profiling, and secondary ion mass spectroscopy. The diffusion coefficients, \(D = D_o e^{ - E_a /kT} \), were derived. For InP, D0=4.82 × 10−2cm2/sec and Ea=1.63 eV and for In0.53Ga0.47As, D0=2.02 × 104cm2/sec and Ea=2.63 eV. Diffusion into the heteroepitaxial structures used in the fabrication of planar PIN photodiodes is dominated by the effects of the InP/InGaAs interface.

Heat-treatment of zinc-coated aluminium

The heat-treatment of zinc-coated aluminium in atmospheric air was studied. The weight gain of the heat-treated zinc-coated aluminium specimens (in the range 250–350°C) was found to increase following a parabolic law with increasing time for constant heating temperature. Zinc oxide (ZnO) of protective nature was found to form on their surface in the range 250–350°C. Heat-treatment at 400°C resulted in the formation of non-protective oxide on the surface of the specimens. Heat-treatment also resulted in the diffusion of zinc into the aluminium substrate and mainly in the diffusion of aluminium into the zinc coating. For high temperatures and large heating times the above procedure resulted in the formation of a two-phase diffusion zone consisting of nearly elemental zinc and aluminium, since the mutual solubility of these two elements is very small.

Correlation factor and concentration profiles for interstitial—substitutional mechanism with impurity—vacancy interaction in the FCC lattice by means of Monte Carlo method

The defect structure induced by zinc diffusion at 1170 K into undoped and indium-doped, semi-insulating GaAs single crystals was characterized for various diffusion times by analytical transmission electron microscopy of cross-sectional specimens. The results were compared with zinc concentration profiles obtained by spreading-resistance measurements on the same samples. Corresponding to zones of different zinc concentrations, three regions of characteristically different defect structures were distinguished. In the diffusion front region, interstitial-type dislocation loops, dislocation networks and gallium precipitates with voids in spatial correlation with the dislocations were found independent of diffusion conditions. The defect structure in the surface region depends on the diffusion conditions and is dominated by zinc-rich precipitates. For longer diffusion times, a transition region is observed where faceted voids and large vacancy-type dislocation loops coexist. A model for the formation of the diffusion-induced defects is presented which is based on the creation of a supersaturation of interstitial gallium atoms by the interstitial-substitutional zinc exchange and a resulting supersaturation of arsenic vacancies during diffusion.

Fabrication of a 1.55-μm VCSEL and an InGaAsP-InP HBT from a common epitaxial structure

A common epitaxial structure is used for the fabrication of a 1.55-/spl mu/m vertical-cavity surface-emitting laser and an InGaAsP-InP heterojunction bipolar transistor (HBT). By selectively applying zinc diffusion directly after growth, the doping type of the HBT cap and emitter is reversed, providing the epitaxial material used for the laser. This enables a similar process to be used for the two devices. Fabricated HBTs show a current gain of 400 at a collector current of 20 mA. Lasers are electrically pumped and operate continuous wave up to -70/spl deg/C.

Diffusion of zinc in commercial Al-Zn alloys under high pressure

The effective interdiffusion coefficients of zinc in commercial Al-Zn alloys are obtained within the temperature range 773 to 883 K under pressures from 0 to 0.41 GPa. From the temperature dependence of the effective interdiffusion coefficients, the activation energies for the 701, 703 and 705 alloys are evaluated to be 125, 124 and 127 kJ/mol respectively, and their pre-exponential factors are 3.0 × 10−5, 4.0 × 10−5, and 3.9 × 10−5 m2/s respectively. The activation volumes, ΔV, for diffusion of zinc in the commercial Al-Zn alloy are 8.30 × 10−6, and 8.60× 10−6 m3/mol at 823 and 883 K, respectively. The ratios of the activation volume to the molar volume of aluminum, ΔV/V0, are 0.83 at 823 K and 0.86 at 883 K. This means that the diffusion of zinc in the commercial Al-Zn alloys occurs predominantly by the monovacancy mechanism at 823 and 883 K.

Point defects in silicon after zinc diffusion - a deep level transient spectroscopy and spreading-resistance profiling study

We present results from spreading-resistance profiling and deep level transient spectroscopy on Si after Zn diffusion at 1294 K. Concentration profiles of substitutional in dislocation-free and highly dislocated Si are described by a diffusion mechanism involving interstitial-substitutional exchange. Additional annealing at 873 K following quenching from the diffusion temperature is required in the case of dislocation-free Si to electrically activate . The formation of complexes of with unwanted impurities upon quenching is discussed. Additional Ni diffusion experiments as well as total energy calculations suggest that Ni is a likely candidate for the passivation of . From total energy calculations we find that the formation of complexes involving Zn and Ni depends on the position of the Fermi level. This explains differences in results from spreading-resistance profiling and deep level transient spectroscopy on near-intrinsic and p-type Si, respectively.

Zinc doping of InP by metal organic vapour phase diffusion (MOVPD)

High p-doping of InP is desirable for buried heterostructure lasers and photodiodes. The maximum hole concentration in zinc doped InP grown by MOVPE is limited to 2×10 18 cm −3. On the other hand, a sealed ampoule diffusion process can be used but this suffers from poor reproducibility and surface morphology. Diffusion of zinc in InP was carried out in a multi wafer MOVPE reactor with DEZn as a precursor. Diffusion temperature, DEZn concentration and diffusion time were optimised to obtain a high hole concentration. In situ annealing was used to activate the zinc. The maximum hole concentration obtained with zinc MOVPD is 8×10 18 cm −3. A specular surface is achieved for all zinc concentrations up to 2×10 19 cm −3. The zinc diffusion depth can be controlled reproducibly from 0.3 to over 3 μm. Depth and doping uniformity over a two inch wafer is comparable to MOVPE growth. Excellent results for InP/InGaAs photodiodes were obtained by local zinc MOVPD on a 2 in wafer.

Biological Water Covers - A Preliminary Assessment

Natural oxidation of sulphide minerals in mine wastes leads to the production of acid mine drainage which is environmentally undesirable. One preferred method to minimize the oxidation of mine residues is to store them under a water cover. Although efficient, water covers might not always stop the oxidation. Inclusion of a biologically active organic layer on top of tailings was considered to further improve the effectiveness of the water cover. The capacity of the organic layer to act as an oxygen barrier and metals confiner was verified with laboratory tests. Diffusion cells were used to assess the capacity of organic materials to consume oxygen and prevent upward diffusion of zinc into the water column. A mixture of algae and duckweed was tested as an organic layer with sand used as a control. The results showed that the organic layer could completely consume oxygen and retain metals. Zinc concentrations in the surface water of the diffusion cells did not exceed lmg/L whereas in the control cells, concentrations were up to 10 mg/L. In Organic cells inoculated with sulphate-reducing bacteria, the Zn concentration in the surface water has been maintained to less than 0.5 mg/L.

Dehydration, Diffusion and Entrapment of Zinc in Bentonite

AbstractInteractions with bentonite are important in the chemical speciation and fate of heavy metals in soils and other ecosystems. The interactions of Zn with bentonite were studied using X-ray diffraction (XRD), dehydration, kinetic and sequential extraction procedures. The species and activity of Zn retained by bentonite were affected markedly by pH. The Zn(OH)+ was retained by bentonite prepared at pH ≥ 6.9. The extent of dehydration of Zn(OH)+-bentonite was higher than that for Zn-bentonite. At a relative humidity of 55.5%, the basal spacing of the Zn(OH)+-bentonite was from 1.21 to 1.26 nm with 1 water sheet and that of the Zn-bentonite was 1.51 nm with 2 water sheets. The greater affinity of Zn(OH)+ for bentonite than Zn was associated with a lower degree of hydration. When an aqueous suspension of Ca-bentonite was incubated with soluble Zn, the concentration of Zn retained by the Ca-bentonite was linearly related to the square root of time. The rate of the interaction was controlled probably by the interlayer diffusion and subsequently by the diffusion into the ditrigonal cavities in bentonite. The Zn retained by bentonite was dehydrated in situ so as to increase the bonding of Zn with surfaces of bentonite. With hydrothermal treatment the retained Zn could diffuse easily into the cavities and transform increasingly to the residual forms that are associated with the entrapped form.

Zinc Diffusion through Lipid Bilayers

Zinc diffusion across liposome bilayers was measured for a set of phosphatidylcholines. These lipids were sonicated to form small unilamellar vesicles in the presence of the metallochromic indicator antipyrylazo III. This chelator sequentially forms two complexes with zinc ion. The rate constant for the first complex formation is shown to increase linearly with zinc concentration. The slope of this line, a [Zn2+]-independent, second-order rate constant, varies with changes in phosphatidylcholine properties. The rate constant is little affected by changes in fluidity as estimated from the reduced temperature [Tr= (Texperimental− Tc)/Tc]. In contrast, the rate constant is directly dependent on lipid oxidation as measured by either a thiobarbituric acid test or a spectrophotometric determination of conjugate dienes. We estimate that zinc diffusion stimulated by lipid oxidation can approach rates observed in hepatocyte zinc transport.

High-power antiguided laser array fabricated without the need for overgrowth

The fabrication of conventional semiconductor antiguided laser array structures involves etching of the array profile followed by an overgrowth step. In this letter, we report the fabrication of an antiguided laser array using zinc diffusion induced intermixing of a superlattice to create the necessary index step. The technique was used to fabricate a five-element, 10-/spl mu/m center, antiguided laser array operating at 0.860 /spl mu/m. The device operated at 1.2/spl times/ diffraction limit to 3-W pulsed (total, both facets) and 1.6-W quasi-continuous-wave (CW) (100-/spl mu/s pulses; total, both facets).

Two-Terminal Monolithic In0.5Ga0.5P/GaAs Tandem Solar Cells with a High Conversion Efficiency of Over 30%

A world-record efficiency of 30.28% has been attained for two-terminal monolithic In0.5Ga0.5P/GaAs tandem solar cells under one-sun air-mass 1.5 global illumination. The cell area has a practical size of 4 cm2. At first, high efficiency In0.5Ga0.5P single junction cells had been developed by improving the minority carrier lifetime. Second, the GaAs single junction cells had been investigated to obtain higher open-circuit voltage. Third, the tandem cell performance had been improved by using an InGaP tunnel junction with AlInP barriers which constitute a double-hetero structure and increase the peak current of the tunnel junction. In addition, the AlInP barrier located beneath the InGaP top cell have been found to be effective for reflecting minority carriers in the top cell and for suppressing the diffusion of zinc from the highly doped tunnel junction toward the top cell during epitaxial growth.

Diffusion of zinc acceptors in InAsP by the metal-organic vapor-phase diffusion technique

Diffusion of zinc acceptors in InAsP by a metal-organic vapor-phase diffusion technique, whereby a low-pressure metal-organic vapor-phase epitaxy with dimethylzinc and phosphine is utilized as an open tube diffusion system, is demonstrated to accurately control the diffusion depth in the submicrometer range. The annealing effect on the zinc diffusion profiles in InAsP was found to be the activation of zinc acceptors similar to that in InP, but the maximum hole concentration of 1×1019 cm−3 for the zinc diffusion in InAsP was achieved.

The discovery and acceptance of the Kirkendall Effect: The result of a short research career

In the 1940s, it was a common belief that atomic diffusion took place via a direct exchange or ring mechanism that indicated the equality of diffusion of binary elements in metals and alloys. However, Ernest Kirkendall first observed inequality in the diffusion of copper and zinc in interdiffusion between brass and copper. This article reports how Kirkendall discovered the effect, now known as the Kirkendall Effect, in his short research career.

Recombination model of the diffusion of zinc in GaAs

Recombination model of the diffusion of zinc in GaAs

The effect of a cap layer on the diffusion of zinc from doped silica films in gallium arsenide

The effect of a cap layer on the diffusion of zinc from doped silica films in gallium arsenide

Acid Buffering a High pH Soil for Zinc Diffusion

The effective use of an aqueous buffer solution of acetic acid and sodium acetate (1.0 M HOAc/ 1.4 M NaOAc, pH = 4.8) to lower the pH of a sand-attapulgite clay mixture from 9.4 to 4.8 is demonstrated. Soil buffering is necessary to prevent precipitation of Zn2+ as Zn(OH)2(s) during zinc diffusion tests. The choice of the acetic acid/sodium acetate buffer solution is based on results of batch-type tests and permeation tests performed to evaluate the soil-mixture pH lowering and buffering capacity of dilute solutions of HNO3 (a strong acid), 0.057 M HOAc (a weak acid), potassium hydrogen phthalate (a pH ∼ 4 buffer), and the 1.0 M HOAc/1.4 M NaOAc buffer solution. Measured values of effective diffusion coefficients D* for zinc on unconfined, compacted test specimens of the buffered soil mixture ranged from 0.54 × 10−6 cm2/s to 6.5 × 10−6 cm2/s. This range of D*-values is within the range of D*-values reported for most reactive inorganic solutes in saturated clay soils and at the lower end of the range of D*-values for zinc in saturated clay soils.

Over 30% efficient InGaP/GaAs tandem solar cells

A two-terminal monolithic InGaP/GaAs tandem solar cell with a new efficiency record of 30.28% is realized with a practical large area of 4 cm2 under one-sun air-mass 1.5 global illumination. We report improvements of the tandem cell performance by introducing a double-hetero (hereafter DH) structure InGaP tunnel junction, in which the InGaP layers are surrounded by high band gap AlInP barriers. The DH structure by AlInP barriers increase the peak current of InGaP tunnel junction. The AlInP barrier directly below the InGaP top cell, which takes the part of a back surface field (hereafter BSF) layer, is found to be considerably effective in reflecting minority carriers in the top cell. The AlInP BSF layer does not only form a high potential barrier but also prevents the diffusion of zinc from a high doped tunnel junction toward the top cell during epitaxial growth. Furthermore, an InGaP tunnel junction reduces the absorption loss, which exists in a GaAs tunnel junction, and increases the photogenerated current in the GaAs bottom cell.

Diffusion of Nickel and Zinc in Germanium

Diffusion of Nickel and Zinc in Germanium

Effects of Source Composition on Diffusion and Solubility of Zinc in Gallium Arsenide

Effects of Source Composition on Diffusion and Solubility of Zinc in Gallium Arsenide