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Epitaxial regrowth techniques, using molecular beam epitaxy, were optimized for the inclusion of submicron diffraction gratings within a vertically resonant structure. Various growth conditions including chemical surface preparation, growth rate, and regrown interfacial structure were studied to determine the quality of the regrown materials and structures. Characteristics such as dislocation density and growth planarity (flatness of the regrown layers) were of particular importance due to the vertical geometry and resonance requirements of the structure. Threading dislocation densities of ≈3×106 cm-2 were measured, by means of transmission electron microscopy, in the regrown structures using optimized regrowth processes. Layer thickness variations, due to growth on nonplanar surfaces (diffraction gratings), were characterized using modeling and optical reflectometry. With these results, inclusion of diffraction gratings has been demonstrated with the accurate control over layer thickness needed for use in vertically oriented devices such as vertical-cavity, surface-emitting lasers, and resonant cavity photodetectors. [ABSTRACT FROM AUTHOR]

Comparing to conventional short-pulse (<30 ns) excimer laser annealing, the extended pulse (374 ns) can provide sufficient thermal energy and time into the Pb(Zr1-xTix)O3 (PZT) thin film to complete the crystallization, whereas the bulk of the material remains at low temperature. In this study, thermal simulation is presented to illustrate the temperature distribution in the specimen and the benefits of the extended pulse. With extended-pulse laser annealing, we observe a 50% improvement in remanent polarization because of the elimination of the amorphous layer on the PZT surface, which is also confirmed by cross-section transmission electron microscopy analysis. This low temperature process is suitable for embedded capacitor-over-interconnect ferroelectric random access memory for advanced system-on-chip applications. [ABSTRACT FROM AUTHOR]

Material integrations of GaN/GaN and Al[sub 0.25]Ga[sub 0.75]N/GaN semiconductors through wafer bonding technology were reported in this work. The wafer surface and interface microstructures were characterized by scanning electron microscopy and energy dispersive x-ray spectroscopy. The interface adhesion (bonding strength) was estimated based upon the interface fracture energy γ[sub o] measured by double-cantilever beam technique. The interface adhesion properties of several different wafer-bonded III-V semiconductors were also compared. By comparing the atomic chemical bond energy E[sub o] with the measured interface fracture energy γ[sub o], the bondability of a few major III-V semiconductors was analyzed. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Polycrystalline (Ga,As) grown by molecular-beam epitaxy (MBE) is compared to polycrystalline (Ga,As) formed by annealing amorphous (Ga,As) also grown by MBE. Both amorphous and polycrystalline materials were grown at 100 °C and crystallinity is controlled by the As overpressure. As the amorphous material was annealed at varying temperatures from 300 to 500 °C several properties of the material changed such as levels of excess As in the material, grain structure of annealed material, strength and adhesion of crystallized layer, and conductivity of the material. After annealing at temperatures around 400 °C, the material is specular, polycrystalline, has good adhesion, and is very conductive. Resistivity values of less than 2 mΩ cm and acceptor concentrations near 5×10[sup 20] cm[sup -3] were detected according to Hall/van der Pauw measurements. Conduction is believed to be due to the large amount of excess As in the material forming an As conduction path when the material is annealed. Material grown in a polycrystalline form by MBE differs in both grain structure and conductivity from material crystallized from an amorphous form. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

High-quality regrowth of In[sub x]Ga[sub 1-x]As and In[sub 0.25]Al[sub 0.75]As layers on In[sub 0.25]Ga[sub 0.75]As pseudosubstrates was demonstrated. These pseudosubstrates were formed using lateral oxidation of an underlying Al[sub 0.98]Ga[sub 0.02]As layer to improve the material quality of a relaxed In[sub 0.25]Ga[sub 0.75]As seeding layer. Using transmission electron microscopy, dislocation densities in the regrown layers were measured and found to be equal to that of the underlying pseudosubstrates (<=10[sup 6] cm[sup -2]). Doping characterization of these regrown films, using Hall-effect measurements, was also performed for both Si-doped and Be-doped materials. The doped In[sub 0.25]Ga[sub 0.75]As films showed normal carrier concentration trends as compared to doped GaAs films and In[sub 0.53]Ga[sub 0.47]As films grown on InP substrates. The doped In[sub 0.25]Al[sub 0.75]As films, however, showed lower-carrier concentrations than expected. In addition, room-temperature photoluminescence (PL) measurements of thick (∼1 μm) In[sub 0.25]Ga[sub 0.75]As layers show emission near 1.1 μm indicating the high quality of the regrown material. Strained In[sub 0.40]Ga[sub 0.60]As quantum wells (QWs) were also grown in an In[sub 0.25]Ga[sub 0.75]As matrix. PL measurements taken at a temperature of 77 K show emission from the strained QWs at a wavelength near 1.23 μm. With further optimization, these materials promise room-temperature emission at wavelengths near 1.3 μm. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

In this study, the interface adhesion and mechanical strength of wafer bonded GaAs/GaAs and GaAs/InP semiconductors, each of (100) face, were characterized by combining the measurements of interface fracture energy γ[sub o] and lap shear strength E[sub s]. The relations between the interface adhesion and annealing processes for four different types of bonding configurations, i.e., antiphase bonding, in-phase bonding, and twist bonding with 5° and 30° misalignments, were systematically studied. The surface free energy γ[sub α-GaAs/oxide] (0.11–0.28 J/m[sup 2]) of amorphous α-GaAs/oxide mixture was estimated based upon the reported surface free energy γ[sub c-GaAs] (0.63 J/m[sup 2]) of crystalline [100] GaAs and measured overall interface fracture energy γ[sub total] (0.525 J/m[sup 2]) of GaAs/GaAs bonded wafers. The micromorphologies of the bonded and debonded wafer interfaces were characterized by atomic force microscopy (AFM) and transmission electron microcopy (TEM). The interface microfailure mechanism of directly bonded GaAs wafers was proposed based on AFM and TEM microstructural analysis. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

In this study, the electrical characteristics and interface microstructures of GaAs-based n-n and p-n interface junctions prepared from direct wafer bonding have been systematically investigated through current-voltage measurements and transmission electron microscopy. It is found that a nearly continuous amorphous interface layer exists in all samples bonded at 400°C. A drastic change in interface morphology caused by atomic rearrangement during high-temperature annealing at 600°C leads to the formation of a locally perfect junction interface combined with an array of nanoscale, bubblelike amorphous regions. Each of them plays a different role in affecting carrier transports. The regions with local crystalline perfection can result in a considerable reduction of interface resistance for the majority carrier transport. However, the non-negligible interface resistance suggests that at interface boundary, there still exits a large number of interface states resulting from atomic imperfections, such as point defects and dangling bonds. On the other hand, the array of nanoscale, bubblelike regions is believed to provide a significant leakage path for minority carriers in p-n junctions. The p-n junction bonded at 400°C exhibits an ideality factor of about 1.9 compared to 1.1 from an epitaxially grown p-n junction. After annealing at 600°C, the increased leakage current along the bubblelike amorphous regions results in a deteriorating ideality factor from 1.9 to 2.5. [ABSTRACT FROM AUTHOR]

Cu-Pt ordering is studied with cross-sectional transmission electron microscopy in p-type, n-type, and nominally undeped InAlP and In(AlGa)P layers. These different doping conditions allow us to investigate the effect of accepter doping with magnesium and donor doping with tellurium on removing Cu-Pt ordering in In(AlGa)P. Even more significant, however, is the ability to investigate the effect of native group III self-diffusion in p-type, n-type, and nominally undeped InAlP and In(AlGa)P layers. Our data indicate that the rapidly diffusing Mg accepter species is less effective on removing Cu-Pt ordering than the relatively slow diffusing Te donor species. Also, our results indicate that the native group III defects and group III self-diffusion play a more important role in removing Cu-Pt ordering than either group II accepter diffusion or group VI donor diffusion. [ABSTRACT FROM AUTHOR]

The strain-induced lateral-layer ordering process was used to fabricate GaInAs quantum wire (QWR) heterostructures on InP whose QWR layers are separated by different barrier materials. Using cross-sectional transmission electron microscopy the microstructure of the different QWR samples was studied. It was found that GaInAs QWR heterostructures with nominally lattice matched AlGaInAs barriers resulted in heavily strained QWR regions relative to the same structure with nominally lattice matched AlInAs or InP barriers. Furthermore, photoluminescence studies demonstrate that these heavily strained QWR samples with AlGaInAs barriers have a wavelength-shift rate of 0.2 to 1.0 Å/°C in the 293–360 K range. This is in comparison to GaInAs QWR samples with ternary or binary barriers and a GaInAs quantum well control sample that have wavelength-shift rates of ∼2.5 and ∼6.0 Å/°C, respectively. It is shown empirically that a minimum amount of strain in the GaInAs QWR/AlGaInAs barrier region is required to achieve wavelength-shift rates below 1 Å/°C. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Amorphous and polycrystalline compounds of (Ga,As) and (Al,As) grown at very low temperatures by molecular-beam epitaxy are characterized. The ultimate microstructure and the amount of excess arsenic incorporated in the (Ga,As) or (Al,As) layers are found to depend on the arsenic overpressure during the low-temperature growth. With lower arsenic overpressure, a polycrystalline structure prevails and less excess arsenic is observed inside the layer. In contrast, a high incorporation of excess arsenic achieved by high-arsenic overpressures leads to the formation of amorphous films. Upon wet oxidation, the lateral oxidation rate of (Al,As) is found to depend on the crystallinity of the (Al,As) layer and the amount of excess arsenic. During the same process, recrystallization proceeds in the (Ga,As) layer. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Presents information on a study which investigated the behavior of arsenic precipitation in low-temperature grown III-V arsenides. Experimental details; Results and discussion; Conclusions.

Focuses on strained-layer resonant tunneling structures of pseudomorphic gallium arsenide-aluminum arsenide-indium. Overview of the energy spectrum of the unbiased structure; Details of tunneling associated with a bound-state energy level; Current-voltage and conductance of the sample.

Deals with a study which examined the impurity-induced layer disordering of Al[subx]Ga[sub1] - [x]arsenic-gallium arsenide quantum-well heterostructures. Experimental procedures; Application of ion implantation to the fabrication process; Structure of superlattice.

Presents a study that used quantum well heterostructure (QWH) wafers to fabricate buried-heterostructure Al[subx]Ga[sub1-x]As-GaAs quantum well lasers using silicon-induced layer disordering. Significance of impurity-induced layer disordering; Impurity redistribution in a QWH; Description of the disorder-defined QWH lasers.

Reports on the effects of arsenic overpressure and diffusion source on the diffusion of manganese in gallium arsenide. Impact of the reaction between the manganese film and the gallium arsenide matrix; Incorporation of the p-dopant in gallium arsenide by diffusion or during molecular beam epitaxy growth; Comparison of various Mn,Ga compounds.

Presents a study that examined the photoluminescence characteristics of n- and p-type pseudomorphic InGaAs-GaAs-AlGaAs single and multiple-quantum-well heterostructures. Experiment conducted; Results; Discussion.

Presents a study which discussed two ways to reduce leakage currents in transverse junction stripe (TJS) lasers. Ways to reduce leakage currents in TJS; Effect of the chemical treatments on the electrical characteristics and laser thresholds of TJS lasers; Reduction of the laser thresholds of lattice-matched TJS lasers.

Describes the incorporation of silicon in locally laser-melted Al[sub x]Ga[sub 1-x]As-GaAs quantum well heterostructures from a thin-film dielectric source. Composition of the melted materials; Examination of doping behavior through secondary-ion mass spectroscopy, electron dispersion X-ray spectroscopy and transmission electron microscopy; Annealing process.

Presents a study which examined the effects of low-temperature annealing on the native oxide of Al[subx]Ga[sub1-x]As formed through water vapor oxidation. Experimental procedures used; Analysis of as-grown and oxidized Al[sub0.8]Ga[sub0.2]As; Reaction between the arsenic and oxide shown by the secondary-ion mass spectrometry oxygen ion counts.

Presents a study which examined Al-Ga interdiffusion, carbon acceptor diffusion and hole reduction in carbon doped Al[sub0.4]Ga[sub0.6]As/GaAs superlattices annealed under different ambient As[sub4] pressure conditions. Experimental details; Results and discussion; Conclusions.

Presents data on the photopumped room temperature continuous operation of native-oxide-embedded quantum-well-heterostructure lasers. Experimental details; Results; Conclusions.

Provides information on hole density in carbon-doped gallium arsenide and aluminum-gallium-arsenic as a function of the annealing temperature. Cause of an increase in lattice parameter of the carbon-doped epilayer; Direct determination of the lattice site location of carbon in samples; Information on the microstructural quality of the film; Use of transmission electron microscopy.

Presents a study that examined carbon-doped gallium arsenide (GaAs) with carbon concentrations grown by metalorganic chemical vapor deposition and metalorganic molecular beam epitaxy. Information on GaAs; Background on carbon; Use of double crystal x-ray diffraction and transmission electron microscopy.

Demonstrates the continuous room-temperature operation of planar index-guided burried-mesa heterostructure visible-spectrum laser diodes. Basis for a system of III-V semiconductor laser lamps with possible wavelengths; Formation of the planar mesa structure; Schematic diagram of the heterostructure laser crystals employed.

Studies the use of gas source molecular beam epitaxy in growing Al[subx]Ga[sub1-x]P mole fractions. Growth procedure; Structural properties of the samples; Electrical properties of the samples.

Describes the deterioration of Al[subx]Ga[sub1-x]As-GaAs heterostructures in long-term exposure to normal room environmental conditions. Experimental procedure; Results of the transmission electron microscopy and electron dispersion x-ray spectroscopy analysis; Conclusions.

Deals with a study which aimed to determine the critical parameters for vacancy- and impurity-induced layer disordering of Al[subx]Ga[sub1-x]As-GaAs quantum-well heterostructure crystals that utilize SiO[sub2] and Si[sub3]N[sub4] diffusion source layers. Experimental details; Results and discussion.

Describes impurity-induced layer disordering experiments on quantum well heterostructures doped with carbon. Importance of crystal surface interaction with ambient and the so-called Fermi-level effect; Determination of the influence of crystal surface stoichiometry on aluminum-gallium interdiffusion.

Presents information on a study which discussed the role of increased crystal defect concentration on donor diffusion and layer intermixing by creating regions of high defect density via a second crystal growth, overgrown crystal, on laser-melted substrates. Growth of crystals by metalorganic chemical vapor deposition; Results of thermal annealing experiments conducted on capless undoped superlattice samples; Factors which contributed to the intermixing of layers near the sample surface.

Presents a study which demonstrated photon-assisted laser operation of photopumped strained-layer Al[suby]Ga[sub1-y]As-Ga-As-In[subx]Ga[sub1-x]As quantum well heterostructures grown using metalorganic chemical vapor deposition. Experimental procedures; Results; Conclusions.

Reports on the diffusion of silicon into quantum-well heterostructures and superlattices employing the high gap III-IV quaternary system In[suby](Al[subx]Ga[sub1-x])[sub1-y]P. Information on layer disordering in the quaternary system; Impurity-induced layer disordering experimental results and analysis.

Focuses on a study which investigated the effects of radio frequency reactor types on gallium arsenide hydrogenation. Experimental procedures; Advantage of using the inductively coupled discharge for hydrogenation of gallium arsenide; Dependence of gallium arsenide plasma etching on parallel-plate reactor.

Presents a study that investigated impurity diffusion and layer interdiffusion in Al[sub x] Ga[sub1-x] As-GaAs heterostructures. Experimental procedure; Results and discussion.

Presents a study that examined gallium arsenide layers grown on misoriented silicon substrates for defect reduction as a function of thermal annealing and degree of misorientation. Experimental techniques; Results; Discussion.

Discusses a study which focused on anomalous threshold current and time delays in index-guided Al[subx]Ga[sub1-x]As-GaAs quantum-well lasers. Event in which quantum-well heterostructures have been found to be unstable against; Capability of the impurity-induced layer disordering; Factor useful in converting initially p-type material to n-type.

Studies the thermal annealing and photoluminescence measurements on aluminum and gallium arsenide compound quantum-well heterostructures (QWH) with selenium and manganese sheet doping. Applications of QWH; Details on the experimental procedures; Discussion on the experimental results.

Deals with a study which showed the effects of dielectric encapsulation and antimony overpressure on aluminum-gallium (Al-Ga) interdiffusion for a quantum-well heterostructure. Experimental procedures; Values for the variation of energy gap; Comparison of structural modifications.

Presents a study that examined the photoluminescence and absorption data on silicon (Si)- and germanium (Ge)-disordered Al[subx]Ga[sub1-x]As-gallium arsenide superlattices. Examination of the disordering of the superlattice; Evaluation of the Si- and Ge-disordered superlattice; Analysis of the transmission electron micrograph of the superlattice.

Describes a form of a buried heterostructure Al[subx]Ga[sub1-x]As-GaAs quantum-well laser. Uses for impurity-induced disordering; Technique used to measure the optical power output.

Reports on the growing of double pulse doped AlGaAs/InGaAs/AlGaAs pseudomorphic high electron mobility transistor on InGaAs substrates using molecular beam epitaxy. Use of strain compensated, AlGaInAs/GaAs superlattice for improved resistivity and breakdown; Obtaining of electrical and optical properties; Growing of PHEMT structures to reduce strain.

Presents a study which dealt with the fabrication of gallium indium phosphide (GaInP) quantum wires. Discussion on the strain-induced lateral-layer ordering mechanism; Integration of laterally confined structures in GaInP; Experimental results.

Presents information on a study that explored the selectively red shifting the photoresponse of intersubband GaAs/Al[sub.25]Ga[sub0.75]As multiple quantum well infrared photodetectors by furnace and rapid thermal annealing. Experimental procedure; Absolute response spectra of the as-grown and annealed quantum well infrared photodetectors; Conclusions.

Provides information on a study that described the spontaneously formed long-range compositional modulation and the related optical property enhancement in aluminum-rich and gallium rich Al[subx]Ga[sub1-x]As/Al[suby]Ga[sub1-y] superlattices in both (111)A and (111)B AlGaAs. Experimental procedure; Results and discussion on the study; Conclusions.

Focuses on a study which examined the effect of growth temperature and the strained short-period superlattice layer thickness on Ga[subx]In[sub1-x]As material system. Methods of preparing quantum wire heterostructure; Effect of temperature; Examination of total strain effect.

Based upon temporal measurements of interface electrical conductivity from current-voltage characterization and interface micromorphologies from transmission electron microcopy, a kinetic analysis of the thermally induced interfacial transformation process of GaAs/GaAs semiconductor interfaces fabricated by wafer bonding technology is performed. The activation energy required for the overall interface transformation that involves defect and atomic diffusion was determined to be 0.75 eV. A physical model of this transformation process is proposed. [ABSTRACT FROM AUTHOR]

Digital Al[SUBx]Ga[SUB1-x] As alloys consisting of a repeated structure of alternating layers ofA1As and GaAs were grown between layers of GaAs. Lateral oxidation characteristics of these digital Al[SUBx]Ga[SUB1-x] As (x>0.8) alloys were determined. Decreasing aluminum compositions resulted in slower oxidation rates, similar to true Al[SUBx]Ga[SUB1-x] As alloys. Further investigations of the oxidation characteristics of a digital Al[SUB0.98]Ga[SUB0.02]As alloy indicate that shorter periods (24.5 monolayers (ML) AlAs/0.5 ML GaAs) showed slower oxidation rates than the longer period alloys (49 ML AlAs/1 ML GaAs or 98 ML AlAs/2 ML GaAs). As the GaAs layers become closer together (that is a digital alloy with a shorter period), the material more closely resembles a true alloy showing slower oxidation rates. Regrowth of an Al[SUB0.3]Ga[SUB0.7] As/GaAs superlattice on the laterally oxidized samples, capped with a thin GaAs layer, was performed. The high-temperature regrowth process caused delamination problems for the oxidized conventional AlAs material, resulting in a rough surface morphology causing a decrease in photoluminescence (PL) intensity. Oxidized digital alloys allowed for a large increase in useable surface area and higher PL intensities, indicating the superiority of the digital Al[SUBx]Ga[SUB1-x]As alloys for regrowth applications. [ABSTRACT FROM AUTHOR]

A novel metallic bonding method using AuGeNiCr as the bonding medium was developed for the fabrication of long-wavelength vertical-cavity surface-emitting lasers (VCSELs). The metallic bonding process can be performed at a low temperature of 320 °C within 1 h and it does not require chemical-mechanical polishing or etching treatments on the bonding surfaces. As determined by atomic force microscopy, the process can tolerate a surface roughness of ∼ 10 nm on the surface of bonding samples. Cross-sectional transmission electron microscopy shows that the bonding interface is smooth and damage-free. Using this bonding technique, a 1.55 µm GalnAsP/InPVCSEL structure with Al-oxide/Si distributed Bragg reflectors was demonstrated on a Si substrate. No degradation was found on the bonded VCSEL structure after annealing at 420 °C. The reflectivity and resonance measured from the bonded VCSEL cavity confirmed the high optical quality provided by this bonding process for device fabrication. [ABSTRACT FROM AUTHOR]

The strain relaxation in In[sub 0.25]Ga[sub 0.75]As and In[sub 0.4]Ga[sub 0.6]As grown on GaAs substrates at low temperature has been studied before and after laterally oxidizing an underlying Al[sub 0.98]Ga[sub 0.02]As layer. The relaxation as a function of layer thickness has been measured by cross-sectional transmission electron microscopy and x-ray analysis. It is found that oxidation of the Al[sub 0.98]Ga[sub 0.02]As layer improves the relaxation of the strained In[sub x]Ga[sub 1-x]As layer. Moreover, the interfacial misfit dislocations have been removed, and the threading dislocation density has decreased approximately by one order of magnitude after oxidation. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]