Erratum

Epitaxial layers of ZnSe ranging in thickness from 5μm to 30 μm have been grown on GaAs (100) substrates over the temperature range 240° C to 340° C by atmospheric pressure MOVPE employing dimethylzinc and hydrogen selenide. An optimum growth temperature of 280 ± 5° C has been identified and when grown at this temperature the ZnSe epitaxial layers exhibit low resistivity (ρ _{298 K} ≤ 10 ohm · cm), a low compensation ratio (θ _{298 K} = 0.27), a carrier mobility (μ _{298 K} ) of 250 ±10 cm ² V ^-1 s ^-1 ) and are n -type ( n _{298 K} = 8.0 × 10 ¹⁴ cm ^-3 ). The ratio of photoluminescence intensity measured at 298K and at 12 K is high (10 ⁴ ) and is dominated by a sharp emission due to excitons bound to neutral donors at 2.7956 eV. Mass spectrometric investigations of the chemical reactions occurring inside the reactor in the presence of the GaAs substrate indicate significant surface-controlled reactivity in the region of 280° C. The online version of the original article can be found at     

Electrical and photo-luminescence properties of ZnSe epitaxial layers grown on GaAs (100) by atmospheric pressure MOVPE: The role of substrate temperature

Epitaxial layers of ZnSe ranging in thickness from 5μm to 30 μm have been grown on GaAs (100) substrates over the temperature range 240° C to 340° C by atmospheric pressure MOVPE employing dimethylzinc and hydrogen selenide. An optimum growth temperature of 280 ± 5° C has been identified and when grown at this temperature the ZnSe epitaxial layers exhibit low resistivity (ρ_{298 K} ≤ 10 ohm · cm), a low compensation ratio (θ_{298 K} = 0.27), a carrier mobility (μ_{298 K}) of 250 ±10 cm²V^-1s^-1) and aren-type (n _{298 K} = 8.0 × 10¹⁴ cm^-3). The ratio of photoluminescence intensity measured at 298K and at 12 K is high (10⁴) and is dominated by a sharp emission due to excitons bound to neutral donors at 2.7956 eV. Mass spectrometric investigations of the chemical reactions occurring inside the reactor in the presence of the GaAs substrate indicate significant surface-controlled reactivity in the region of 280° C.     

Development of (Bi,Sb)<Subscript>2</Subscript>(Te,Se)<Subscript>3</Subscript>-Based Thermoelectric Modules by a Screen-Printing Process

In major applications, optimal power will be achieved when thermoelectric films are at least 100 μm thick. In this paper we demonstrate that screen-printing is an ideal method to deposit around 100 μm of (Bi,Sb)₂(Te,Se)₃-based films on a rigid or flexible substrate with high Seebeck coefficient value (90 μV K⁻¹ to 160 μV K⁻¹) using a low-temperature process. Conductive films have been obtained after laser annealing and led to acceptable thermoelectric performance with a power factor of 0.06 μW K⁻² cm⁻¹. While these initial material properties are not at the level of bulk materials, the complete manufacturing process is cost-effective, compatible with large surfaces, and affords a mass-production technique.     

The growth of GaAs,AIGaAs, InP and InGaAs by chemical beam epitaxy using group III and V alkyls

The growth kinetics of chemical beam epitaxy (CBE) were investigated with the growth of GaAs, AIGaAs, InP, and InGaAs. Results obtained with epilayers grown by using trimethylarsine (TMAs) and triethylphosphine (TEP) instead of arsine (AsH3) and phosphine (PH₃) were reviewed with some additional results. The CBE grown epilayers have similar optical quality to those grown by molecular beam epitaxy (MBE). Superlattices of GaAs/AlGaAs with abrupt interfaces have been prepared. Since trimethylindium (TMIn) and triethylgallium (TEGa) used in the growth of InGaAs emerged as a single mixed beam, spatial composition uniformity was automatically achieved without the need of substrate rotation in the InGaAs epilayers grown. Lattice-mismatch Δα/α< 1 x 10^-3 have been reproducibly obtained. For epilayers grown with high purity TMAs source, room-temperature electron mobility as high as 9000 cm²/V sec and concentrations of ˜7 x 10¹⁵ cm^-3 were produced. In general, the electron mobilities were as good as those obtained from low-pressure metalorganic chemical vapor deposition. (MO-CVD). Unlike MBE, since the In and Ga were derived by the pyrolysis of TMIn and TEGa molecules at the heated substrate surface, respectively, oval defects observed in MBE grown epilayers due to Ga splitting from Ga melt were not present in CBE grown epilayers. This is important for integrated circuit applications. Unlike MO-CVD, the beam nature of CBE allows for selective area growth of epilayers with well-defined smooth edges using mask shadowing techniques. Typically, growth rates of 2-5μm/h for InP, 2-6μm/h for GaAs and AIGaAs, and 2-5μm/h for InGaAs were used.     

Selective etch-back and growth of InGaAs ON (100) Fe:lnP by electroepitaxy

Selective etch-back prior to growth of InGaAs islands on SiO₂-masked (100)Fe-doped InP substrates was performed by electroepitaxy. The etch-back of the substrate and the growth of the layer was done at a constant furnace temperature of 640° C by passing a direct electric current from the melt to the substrate for etch-back and from the substrate to the melt for growth. The current density used was 1 to 20 A/cm² for a period from 15 to 60 min. The isolated InP regions were of various sizes (40 × 1000μm to 3000 × 3000μm), and different geometries (narrow and wide strips, square, circular). A uniform etch-back and uniform growth with excellent surface morphology was obtained on strips as wide as 200μm and on circles withd < 500μm. For islands with wider geometry, growth as well as etch-back were uniform up to 100–200μm from the periphery with excellent surface morphology. The etch-back and growth profiles are trapezoid-shaped and are not influenced by the difference in chemical activity between crystalline planes. The orientation dependence of the etch rate was {110} > {100} > {011} > {111} B > {111} A.     

Comparison of MBE Growth of InSb on Si (001) and GaAs (001)

We describe the epitaxial growth of InSb films on both Si (001) and GaAs (100) substrates using molecular-beam epitaxy and discuss the structural and electrical properties of the resulting films. The complete 2 μm InSb films on GaAs (001) were grown at temperatures between 340°C and 420°C and with an Sb/In flux ratio of approximately 5 and a growth rate of 0.2 nm/s. The films were characterized in terms of background electron concentration, mobility, and x-ray rocking curve width. Our best results were for a growth temperature of 350°C, resulting in room-temperature mobility of 41,000 cm²/V s.  For the growth of InSb on Si, vicinal Si(001) substrates offcut by 4° toward (110) were used. We investigated growth temperatures between 340°C and 430°C for growth on Si(001). In contrast to growth on GaAs, the best results were achieved at the high end of the range of T _S =  C, resulting in a mobility of 26,100 cm²/V s for a 2 μm film. We also studied the growth and properties of InSb:Mn films on GaAs with Mn content below 1%. Our results showed the presence of ferromagnetic ordering in the samples, opening a new direction in the diluted magnetic semiconductors.     

Component Overpressure Growth and Characterization of High-Resistivity CdTe Crystals for Radiation Detectors

Spectrometer-grade CdTe single crystals with resistivities higher than 10⁹ Ω cm have been grown by the modified Bridgman method using zone-refined precursor materials (Cd and Te) under a Cd overpressure. The grown CdTe crystals had good charge-transport properties (μτ _e = 2 × 10⁻³ cm² V⁻¹, μτ _h = 8 × 10⁻⁵ cm² V⁻¹) and significantly reduced Te precipitates compared with crystals grown without Cd overpressure. The crystal growth conditions for the Bridgman system were optimized by computer modeling and simulation, using modified MASTRAPP program, and applied to crystal diameters of 14 mm (0.55′′), 38 mm (1.5′′), and 76 mm (3′′). Details of the CdTe crystal growth operation, structural, electrical, and optical characterization measurements, detector fabrication, and testing using ²⁴¹Am (60 keV) and ¹³⁷Cs (662 keV) sources are presented.     

Epitaxial growth of garnets for thin film lasers

Liquid phase epitaxial techniques have been developed for the preparation of thin films of optical materials. Heteroepitaxy of magnetic garnets on nonmagnetic garnet substrates by the dipping technique employs the phenomenon of stable supersaturation in the iron garnet-PbO:B₂O₃ system. Rare earth aluminum garnets in the same flux supersaturate to a lesser extent and precipitate readily upon substrate insertion. High quality films of YAG:Nd and YAG:Yb,Er,Tm,Ho on pure YAG as well as pure YAG on YAG:Nd have been prepared from a saturated PbO:B₂O₃₊ flux using a transfer technique. Laser oscillation of Ho³⁺ at 2.1μm and Nd³⁺ at 1.06μm in single crystal epitaxial films prepared by the transfer technique have been reported by van der Ziel et al. Solute transfer has the advantage in optic garnet systems of uniform film growth at constant temperature without spontaneous nucleation. In addition, continuous solution of uniform composition nutrient maintains the rare earth dopant concentration in the melt. Pb incorporation results in a brown discoloration but can be eliminated by the proper choice of growth temperature. Deposition rates between 2 μm and 6 μm/hr. at ∼1O00°C have been found satisfactory. In this paper melt preparation, furnace design, the effect of impurities on threshold, and the effects of lattice mismatch and substrate orientation will be discussed.     

Photovoltaic detector based on type II heterostructure with deep AlSb/InAsSb/AlSb quantum well in the active region for the midinfrared spectral range

Photodetectors for the spectral range 2–4 μm, based on an asymmetric type-II heterostructure p-InAs/AlSb/InAsSb/AlSb/(p, n)GaSb with a single deep quantum well (QW) or three deep QWs at the heterointerface, have been grown by metal-organic vapor phase epitaxy and analyzed. The transport, luminescent, photoelectric, current-voltage, and capacitance-voltage characteristics of these structures have been examined. A high-intensity positive and negative luminescence was observed in the spectral range 3–4 μm at high temperatures (300–400 K). The photosensitivity spectra were in the range 1.2–3.6 μm (T = 77 K). Large values of the quantum yield (η = 0.6−0.7), responsivity (S _λ = 0.9−1.4 A W^–1), and detectivity (D* _λ = 3.5 × 10¹¹ to 10¹⁰ cm Hz^1/2 W⁻¹) were obtained at T = 77–200 K. The small capacitance of the structures (C = 7.5 pF at V = −1 V and T = 300 K) enabled an estimate of the response time of the photodetector at τ = 75 ps, which corresponds to a bandwidth of about 6 GHz. Photodetectors of this kind are promising for heterodyne detection of the emission of quantum-cascade lasers and IR spectroscopy.     

The influence of supercooling on the liquid phase epitaxial growth of inas1−xsbx on (100) GASB substrates

The growth by liquid-phase epitaxy of InAs_1−x Sb _x (x = 0.08-0.16) on GaSb was accomplished by using melts of constant arsenic concentration x _As ^L = 0.014. The study of the influence of the degree of supercooling ΔT on the crystal growth was investigated. The strong tendency of the In-As-Sb liquid to dissolve the GaSb substrate was resolved by using high ΔT (20-30° C) for layers having a positive lattice-mismatch Δa/a more than 1.5 x 10⁻³. As positive lattice-mismatch becomes smaller, a larger supersaturation is required to control the substrate dissolution. But owing to the bulk nucleation which restricts the supercooling ΔT at values near 30° C, the growth of epitaxial layers with small lattice-mismatch (until - 5 × 10⁻⁴) was achieved only from time to time. It was observed that an increase of ΔT increases the concentration of antimony in the epilayers and hence leads to the lattice-mismatch. The dislocation etch pit density was found to be only dependent on the lattice-mismatch. The thickness of the grown layers is proportional to ΔT xt ^1/2 with a factorK = 0.025 μm . °C⁻² . s^−1/2     

Silver Particle Carbon-Matrix Composites as Thick Films for Electrical Applications

Silver particle (3 μm) carbon-matrix composites in the form of thick films (around 100 μm thick) on alumina, as prepared from pastes comprising silver and mesophase pitch particles (14 μm), have been attained. The films on alumina were fired at 650°C in nitrogen to convert pitch to carbon. The volume electrical resistivity attained ranged from 10⁻⁵ Ω cm to 10⁴ Ω cm, depending on the silver volume fraction. The percolation threshold was 12 vol% silver.     

The sulfur incorporation and the growth of GaAs submicrometer epilayers in Ga-AsCl3-H2 system

Submicrometer epilayers have been grown in Ga-AsCl₃-H₂ system using elemental sulfur as a dopant. The mechanism of sulfur incorporation was discussed on the basis of surface adsorption. It has been shown that the electrical properties of single epilayers are typicallyn=1–2×10¹⁷/cm², thickness 0.4 μm and breakdown voltage about 7–10V. The width of interface region in single and multilayer structures is about 0.1μm. The epilayers obtained have been used to fabricate the microwave devices, such as Gunn diodes, varactors, and far infrared detectors.     

Deposition of Bismuth Telluride Thick Film by Solidification under Centrifugal Pressure

Bismuth telluride alloys—Bi_0.5Sb_1.5Te₃ and Bi_1.8Sb_0.2Te_3.33Se_0.17—have been deposited on polycrystalline zirconia via solidification under centrifugal pressure. The crystal growth under centrifugal pressure was a process in which the starting powders charged in the groove patterns of the substrates were first melted and then solidified under centrifugal acceleration of 10⁴ m/s². This new process offers c-axis-oriented films with a thickness of more than 100 μm. A mirror-like surface is another characteristic feature of these films. Owing to their orientation, reasonable power factors such as 4.2 mW/m K² and 2.7 mW/m K² (in plane) were obtained for p- and n-type films, respectively.     

Low-Resistance Cu-Sn Electroplated–Evaporated Microbumps for 3D Chip Stacking

Low-resistance copper-tin (Cu-Sn) microbumps, with sizes varying from 5 μm × 5 μm to 20 μm × 20 μm and formed by electroplating–evaporation bumping (EEB) technology for three-dimensional integration of large-scale integrated chips, have been evaluated for their microstructure and electrical resistance. It was inferred from x-ray diffraction data that the formation of low-resistance Cu₃Sn intermetallic compound (IMC) is facilitated at higher bonding temperature. Electron probe microanalysis mapping showed that, even before bonding, Cu-Sn IMCs were formed at the interface between Cu and Sn, whereas they were sandwiched between the Cu of the upper and lower microbumps after bonding. Electron backscatter diffraction analysis revealed that the crystal orientation of Sn grains was sharply localized in the (100) orientation for physical vapor deposited (PVD) sample, while electroplated Sn film exhibited a mixed crystal orientation in all (100), (110), and (001) axes. A resistance value of ~35 mΩ per bump was obtained for Cu-Sn microbumps with area of 400 μm², which is several times lower than the resistance value reported for Cu-Sn microbumps fabricated by a pure electroplating method. The low resistance value obtained for EEB-formed Cu-Sn microbumps after bonding is explained by (i) the reduced surface roughness for evaporated Sn, (ii) the high degree of crystal grain orientation resulting from layer-by-layer growth in the PVD Sn, despite their smaller grain size, and (iii) the absence of impurity segregation at grain boundaries.     

Curved crystal spectrometer for the measurement of X-ray lines from laser-produced plasmas

In order to diagnose the laser-produced plasmas, a focusing curved crystal spectrometer has been developed for measuring the X-ray lines radiated from a laser-produced plasmas. The design is based on the fact that the ray emitted from a source located at one focus of an ellipse will converge on the other focus by the reflection of the elliptical surface. The focal length and the eccentricity of the ellipse are 1350 mm and 0.9586, respectively. The spectrometer can be used to measure the X- ray lines in the wavelength range of 0.2-0.37 nm, and a LiF crystal （200） （2d = 0.4027 nm） is used as dispersive element covering Bragg angle from 30° to 67.5°. The spectrometer was tested on Shengnang- Ⅱ which can deliver laser energy of 60-80 J/pulse and the laser wavelength is 0.35 μm. Photographs of spectra including the 1 s2p ^1P1-1s^2 ^1S0 resonance line（w）, the 1s2p ^3P2-1s^2 1S0 magnetic quadrupole line（x）, the 1s2p ^3P1-1 s^2 ^1S0 intercombination lines（y）, the 1 s2p ^3S~1-1 s^2 ^1S0 forbidden line（z） in helium-like Ti Ⅹ Ⅺ and the 1 s2s2p ^2P3/2-1 s622s ^2S1/2 line（q） in lithium-like Ti Ⅹ Ⅹhave been recorded with a X-ray CCD camera. The experimental result shows that the wavelength resolution（λ/△ 2） is above 1000 and the elliptical crystal spectrometer is suitable for X-ray spectroscopy.     

Fabrication of Metal–Oxide–Diamond Field-Effect Transistors with Submicron-Sized Gate Length on Boron-Doped (111) H-Terminated Surfaces Using Electron Beam Evaporated SiO<Subscript>2</Subscript> and Al<Subscript>2</Subscript>O<Subscript>3</Subscript>

A H-terminated surface conductive layer of B-doped diamond on a (111) surface was used to fabricate a metal–oxide–semiconductor field-effect transistor (MOSFET) using an electron beam evaporated SiO₂ or Al₂O₃ gate insulator and a Cu-metal stacked gate. When the bulk carrier concentration was approximately 10¹⁵/cm³ and the B-doped diamond layer was 1.5 μm thick, the surface carrier mobility of the H-terminated surface on the (111) diamond before FET processing was 35 cm²/Vs and the surface carrier concentration was 1.5 × 10¹³/cm². For the SiO₂ gate (0.76 μm long and 50 μm wide), the maximum measured drain current at a gate voltage of −3.0 V was −75 mA/mm and the maximum transconductance was 24 mS/mm, and for the Al₂O₃ gate (0.64 μm long and 50 μm wide), these features were −86 mA/mm and 15 mS/mm, respectively. These values are among the highest reported direct-current (DC) characteristics for a diamond homoepitaxial (111) MOSFET.     

A study of x-ray damage effects on the short channel behavior of IGFET’s

Ionizing particles and radiation may play an important, albeit undesirable role in the processing of VLSI and ULSI circuits in that they can generate bulk charge in the gate insulator of IGFETs. In this regard, there is conflicting information in the literature on the effects of ionizing radiation on short channel phenomena in IGFETs. For example, Peckeraret al. in 1983 claimed that the effective channel length increases when positive coulombic charge is introduced during irradiation, resulting in a decrease in the short channel effect. Schrankleret al. in 1985 claimed in an experimental study, on the other hand, using 28.0 nm thick gate oxides and 0.9–10 μm channel lengths, that the effect is increased,i.e., the short channel effect begins at longer channel lengths. Wilson and Blue in 1982, in a theoretical study concluded that other than a uniform downward shift in theV _T -channel length curve due to the presence of insulator net fixed positive charge, no effect should be observed. Because of these conflicting reports, it was decided to evaluate this behavior using two different background doping levels inn-channel structures, with physical channel lengths ranging between 1.5 and 10 μm, in 0.1 and 0.5 gWcm (100) Si. To further explore the situation, gate oxide (grown at 1000° C in O₂ containing 4.5% HC1) thicknesses were varied from 17.0–35.0 nm, and the absorbed radiation dose using Al-K_α (1.5 keV) x-rays was varied between 2.4 × 10⁶ rad (SiO₂) and 2.4 × 10⁷ rad (SiO₂). For all conditions studied above, a uniform downward shift in the V_T-Channel length curve was observed, essentially corroborating the theoretical conclusions of Wilson and Blue. In addition to the above, the effects of intentionally doping the gate insulator with boron (1.2 × 10¹² B⁺ cm⁻²) implanted at 8 and 10 keV into 25.0 nm and 31.4 nm oxides, respectively, on short channel effects were evaluated for devices grown onp-type 0.5 Ω.cm substrates. Unlike the devices which did not have excess boron intentionally implanted into the gate insulator, it was found that higher concentrations of boron (2.0 × 10¹⁷ cm⁻³ in the insulator via implantation as compared to 4.2 × 10¹⁶ cm⁻³ incorporated in oxides during the oxide growth on 0.5 Ω.cm type (100) Silicon) leads to smaller short channel effects in unirradiated devices. On the other hand, these heavily doped oxides show a distinct worsening of the short channel effect after exposure to 2.4 × 10⁷ rad (SiO₂) using Al-K_α radiation. Thus, while normal devices exhibit little if any short channel improvement, or degradation following irradiation, intentionally doped insulators show an improvement in short channel characteristics prior to irradiation, and a worsening of the short channel effect following irradiation.     

Growth and properties of Hg1-xCdxTe on GaAs,with x − 0.27

The organometallic vapor phase epitaxy of HgCdTe onto (100)2°-(110) GaAs substrates is described in this paper. A buffer layer of CdTe has been grown prior to the growth of HgCdTe, to take up the large lattice mismatch with the GaAs. Considerations for the thickness of this buffer layer are outlined, and it is shown by quantitative Secondary Ion Mass Spectroscopy that there is negligible diffusion of gallium from the GaAs substrate for the growth conditions described. Hall effect measurements give mobilities comparable to those reported for bulk grown crystals. An extrinsicn-type carrier concentration of 2 × 10¹⁶/cm³ is obtained, and is mainly due to residual impurities in the starting chemicals. The alloy composition has been determined at 298 K by Fourier transform infrared transmission (FTIR) spectrometry; this is found to be extremely uniform over a 15 × 7 mm area, as evidenced by an overlapping of FTIR plots taken over this area. HgCdTe layers have been grown on buffer layers varying in thickness from 0.1 to 1.9μm. It is found that a buffer thickness of about 1.9μm or larger is required to obtain high quality HgCdTe, both in terms of the electrical characteristics (mobility and carrier concentration) and the infrared transmission curves (peak transmission).     

Pulsed Electroplating: a Derivate Form of Electrodeposition for Improvement of (Bi1?xSbx)2Te3 Thin Films

Bismuth antimony telluride (Bi_1−x Sb _x )₂Te₃ thermoelectric compounds were synthesized by pulse plating. Due to the large number of parameters available (pulse waveform, on/off pulse time, applied current density), this advanced form of electrodeposition allows better control of the interfacial supply and electrochemical reactions and offers effective ways to improve macroscopic properties such as adhesion and to produce crack-free hard deposits and fine-grained films with higher uniformity and lower porosity. The influence of pulse parameters (pulse time t _on, cathodic current density J _c) on the stoichiometry, roughness, and crystallography of deposits was studied. The thermoelectric properties (electrical resistivity and Seebeck coefficient) of the films were measured. The results revealed that deposits have p-type conductivity directly after electroplating (Seebeck coefficient around 150 μV K⁻¹), in contrast to films synthesized by direct current, which require annealing. An improvement of resistivity was observed: for a direct-current-deposited film the resistivity is around 5000 μΩ m, whereas for a pulse-deposited film the resistivity was around 200 μΩ m.     

Interfacial Reaction Between Eutectic Sn-Pb Solder and Electroplated-Ni as well as Electroless-Ni Metallization During Reflow

Electroplated-Ni (EP-Ni) has been adopted gradually as an underbump metallization layer due to its comparatively lower resistivity and higher deposition rate. In this study, the metallurgical reaction between eutectic Sn-Pb solder and EP-Ni as well as electroless-Ni (EL-Ni) was investigated at 200°C, 210°C, 220°C, and 240°C. It is found that the growth rate of Ni₃Sn₄ intermetallic compound (IMC) on EP-Ni was slower than that on EL-Ni. The consumption rate is measured to be 0.97 × 10⁻³ μm/s and 1.48 × 10⁻³ μm/s for EP-Ni and EL-Ni, respectively. The activation energy is determined to be 51 kJ/mol and 48 kJ/mol for EP-Ni and EL-Ni, respectively. The dense structure of EP-Ni may be responsible for the lower IMC formation rate.