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Evanescent-wave tunneling of visible light is shown to be sensitive to the nanometer air gaps between dielectrics of high refractive indices. The narrow air gap in molecular-force bonded GaP/GaP was then measured to be 1.3 nm.

An approach to image localized and propagating surface plasmon (SP) modes is introduced. It is shown that scanning tunneling microscope (STM)-electroluminescence, the radiative decay of SPs induced by inelastically tunneling electrons, observed in Fourier space yields distinct features that reflect the degree of delocalization and spatial distribution of SP modes. The propagating SP is isolated from the localized mode by way of this Fourier space imaging approach. Furthermore, a cylindrically symmetric spatial interference pattern is obtained when the STM-induced plasmon is created within a circular “corral” boundary condition.

Liquid surface tension has been used to pull different semiconductor wafers to very close contact and strong bonding. Bonded wafers, such as GaAs/GaP, were heat treated without pressure application to achieve wafer fusion. The bonding process has been analyzed, and criteria for surface tension, wafer flatness, and elasticity have been derived.

The photon emission yield observed in scanning tunneling microscopy (STM) measurements of Au hemispheroid-decorated thin films is used to elucidate the interaction of tunneling electrons with local surface plasmon modes. The photon emission probability is found to depend on the surface feature size. The agreement of a model calculation with the experimental results demonstrates that inelastic electron tunneling is the dominant mechanism of STM-induced plasmon excitation for 10–60 nm size metallic features.

Light scattering by edge dislocations and the resulting loss coefficient have been modeled for GaN layers. Phase‐front deformation caused by the refractive‐index variation in the dislocation’s strain field has been considered and the resulting scattering loss calculated. We show that the high dislocation densities observed in recent GaN layers can result in significant large loss coefficients. The present work also offers some insights for improved lasers.

Double‐heterostructure diode lasers emitting at ∼3.9 μm have exhibited pulsed operation at temperatures up to 170 K and cw operation up to 105 K, with single‐ended cw output power of 30 mW at 70 K. The laser structure, grown on GaSb substrates by molecular‐beam epitaxy, has an InAsSb active layer and AlAsSb cladding layers. The lowest pulsed threshold current density is 36 A/cm2 obtained at 60 K. The characteristic temperature is 20 K over the entire temperature range.

Highly precise f/0.9 refractive anamorphic microlenses have been fabricated in GaP substrates by mass‐transport smoothing of etched multiple‐mesa structures. Astigmatic outputs from tapered unstable‐resonator lasers have been collimated to a nearly round beam of near diffraction‐limited 0.43° divergence. Initial good efficiencies (as high as 35%) have been obtained in coupling the laser output into a single‐mode fiber. These lenses are highly promising for realizing simple compact optical systems that exploit the high power capability of tapered lasers.

A new strained‐layer multiple‐quantum‐well (MQW) heterostructure comprising InAs1−xSbx wells and In1−yGayAs barrier layers is proposed for improved 4–5 μm lasers. Both well and barrier compositions are close to InAs and are potentially well suited for high‐quality crystal growth of MQWs on either InAs or GaSb substrates. Simple modeling shows favorable valence‐band alignment suitable for carrier confinement, free of the staggered band alignment problem generally found in the conventional designs. Perturbation calculation of the effect of the compressive strain in the wells also shows sufficient valence subband separation. This and the reduced hole mass are expected to considerably lower the threshold carrier density and Auger recombination.

We report the characteristics of p-channel thin film transistors (p-TFTs) with ZnO/hydrated polyvinyl alcohol (PVA) (ZnO/PVA) conducting channels. The metal-oxide-semiconductor structure of the p-TFTs was composed of indium tin oxide (ITO)/SiO2/ZnO/PVA layers. The TFT was assembled using PVA gel, which was glued to ITO substrates patterned to form source and drain electrodes. The ZnO/PVA composite film acted as an effective conducting film because of the chemisorption reaction at the film interface where free electrons can be generated. The formation of the conducting channel was also affected by VG applied to the TFT. The ZnO/PVA-based TFTs demonstrated p-channel transistor performance, shown by current-voltage (I-V) data analysis. The electrical parameters of the device were evaluated, including the on/off ratio (∼103), threshold voltage (Vth, −1 V), and subthreshold swing (−2.2 V/dec). The PVA/ZnO-based p-TFTs were fabricated using simple and cost-effective approaches instead of doping methods.

Buried‐heterostructure quantum‐well lasers fabricated by mass transport are reported for In0.18Ga0.82As/GaAs/Ga0.5In0.5P strained‐layer structures grown by atmospheric pressure organometallic vapor‐phase epitaxy. Threshold current densities as low as 85 A/cm2 are measured for broad‐stripe lasers, and buried‐stripe devices show threshold currents as low as 3 mA and differential quantum efficiencies as high as 34% per facet without coatings.

Slow evaporation of In from InP wafers has been investigated and identified as a major cause of surface roughness in thermal annealing and mass transport under sufficient phosphorus vapor protection. An analysis shows that In evaporation can be prevented by covering the wafer during the annealing process. However, the commonly used graphite cover by itself is inadequate protection because In vapor is able to permeate the graphite. On the other hand, InP covers alone result in problems caused by the mass transport that occurs between the InP wafer and cover. A covering scheme has been developed that uses InP covers and a quartz enclosure in addition to the graphite cover. This arrangement provides effective wafer protection permitting smooth wafer surfaces to be obtained reproducibly.

A new surface‐emitting diode laser has been demonstrated, which consists of a buried‐heterostructure waveguide gain region on one side of the substrate and a bifocal microlens of 210 μm diameter on the other side. The bifocal microlens is composed of a collimating lens in the center (70 μm diameter) and a spherical mirror in the surrounding region, for output collimation and optical feedback, respectively. Accurate alignment between the gain region and the microlens has been obtained by using the focused light spot produced by the latter. Initial device results show room‐temperature pulsed threshold currents around 92 mA (with a low of 70 mA) and far‐field patterns with a narrow central lobe of 1.25°.

Centimeter‐size single‐crystal InP or GaAs wafers have been fused together entirely, face to face or side by side, after a heat treatment in a graphite/quartz reactor which can press the wafers together through differential thermal expansion. Diodes formed by fusing p‐ and n‐type wafers showed normal current‐voltage characteristics and light emission. Fusion between lattice‐mismatched wafers (i.e., InP and GaAs) has also been demonstrated.

Mass transport of a semiconductor alloy has been demonstrated using Ga0.51In0.49P which is lattice matched to GaAs. Buried‐heterostructure diode lasers with Ga0.51In0.49P as cladding and GaAs as the active layer have been made using this fabrication technique. Initial attempts produce devices with room‐temperature lasing thresholds of ∼33 mA and 15% differential power efficiency per facet.

Blocks of silicon up to 3-mm thick have been formed by directly bonding stacks of thin wafer chips. These stacks showed significant reductions in the thermal conductivity in the bonding direction. In each sample, the wafer chips were obtained by polishing a commercial wafer to as thin as 36 {micro}m, followed by dicing. Stacks whose starting wafers were patterned with shallow dots showed greater reductions in thermal conductivity. Diluted-HF treatment of wafer chips prior to bonding led to the largest reduction of the effective thermal conductivity, by approximately a factor of 50. Theoretical modeling based on restricted conduction through the contacting dots and some conduction across the planar nanometer air gaps yielded fair agreement for samples fabricated without the HF treatment.

Zinc oxide nanodonuts have been synthesized using vapor-phase transport method. Zinc oxide powder, graphite powder, and erbium oxide powder were mixed with a molar ratio of 1:1:0.2 and heated at 1050°C in a flowing argon environment. Perfectly donut-shaped nanostructures with outer diameters ranging from 450to850nm were observed. The inner diameter of the zinc oxide donut varies from 75to95nm and the vertical distance from the highest point to the lowest point vary from 85to130nm. The composition of the nanodonut was analyzed using Auger electron spectroscopy and was found to be mainly of zinc oxide. Diffusion of silicon into the zinc oxide layer was confirmed by secondary ion mass spectroscopy.

Ion backscattering spectrometry has been used to investigate the depth dependence of atomic mixing induced by ion beams. Samples consisting of a thin Pt (or Si) marker a few tens of angstroms thick buried at different depths in a deposited Si (or Pt) layer were bombarded with Xe+ of 300 keV at 2×10^16 cm^–2 dose and Ar+ of 150 keV at 5×10^15cm^–2 dose. Significant spreading of the marker was observed as a result of ion irradiation. The amount of spreading was measured as a function of depth of the marker, which was then compared with the deposited energy distribution. Measurements of this kind promise new insight into the nature of the interaction between ion beams and solids.

A buried‐heterostructure laser has been developed whose output is deflected to a direction perpendicular to the substrate surface by a monolithically integrated 45° (parabolic) mirror. The latter is fabricated by smoothing a chemically etched multistep structure using a mass‐transport phenomenon. The present devices show threshold current as low as 12 mA, differential quantum efficiency as high as 47% and a surface‐emitting far‐field pattern with a main lobe as narrow as 12°.

GaInAsP/InP distributed feedback lasers have been fabricated with a simple new design in which the grating is etched into the top of a mass‐transported buried heterostructure. Single‐frequency operation with sidemodes lower than −32 dB and threshold currents as low as 16 mA have been achieved.

Buried‐heterostructure actively Q‐switched diode lasers have been made with threshold currents as low as 14 mA. The lasers operate continuously at room temperature. Modulation has been observed at rates up to 10.5 GHz. Evidence of several modes of Q switching has been obtained.

We have investigated the pulsation behavior of InGaAsP semiconductor lasers with a proton‐bombarded segment. These lasers emit picosecond (30–70 ps) pulses at gigahertz (0.6–3.0 GHz) rates. An antireflection‐coated diode in an external cavity is passively mode locked and multistable; as many as four co‐existing states are observed. Interlocking hysteresis loops are observed in the pulsation frequency, pulse width, and output power as functions of the bias current. A delayed feedback model explains qualitative features of the multistable mode locking. To our knowledge this is the first report of multistability of laser pulsation.

Argon bubble formation has been observed by Rutherford backscattering spectrometry and cross‐sectional transmission electron microscopy in PtSi sputtered by Ar ions of 20–160 keV. The backscattering data show the bubble formation process to be repetitive. This phenomenon is interpreted in terms of Ar release due to the sputter etching.

Compositional changes of binary alloys and compounds have been observed (by Rutherford backscattering techniques) as a result of rare‐gas sputtering in the energy range 20–80 keV. After sputtering, the heavier components were generally found to be enriched in a surface layer whose thickness corresponded approximately to the range of the sputtering ion; the compositions of these enriched surface layers were independent of the mass and energy of the sputtering ions. This phenomenon of surface layer enrichment is interpreted as due to preferential sputtering from the surface in combination with defect‐enhanced diffusion.

Diffraction‐coupled arrays of InGaAsP/InP buried‐heterostructure lasers are reported. These arrays, fabricated by ion beam assisted etching and mass transport, have a novel scalloped mirror at the end of the coupling section that greatly increases the coupling between stripes and reduces the feedback into the same stripe. Far‐field patterns show sharply defined lobes that are as narrow as 3°. An output section with cylindrical mirrors has been incorporated into the arrays to increase the power in the central far‐field lobe. Threshold currents as low as 150 mA have been obtained for eight‐stripe arrays.

Lenslets with diameters up to 130 μm and numerical apertures of 0.39–0.75 have been formed in InP substrates by using mass transport to smooth out chemically etched multilevel mesa structures. The lenslets show a smooth surface with an accurately controlled profile (i.e., curvatures) and are capable of forming clear images. Some lenslets (with a diameter of approximately 67 μm) have been used to collimate the output of a buried‐heterostructure diode laser (of 1.3 μm wavelength) and resulted in a nearly diffraction‐limited beam divergence of 1.4°.

Two‐dimensional arrays of 16 laser elements have been fabricated using the mass transport process. Good uniformity, low threshold current (typically 11–14 mA per element), and high total cw power (up to 0.27 W at 22 °C) were obtained.

Ion‐beam‐assisted etching has been used to fabricate mass‐transported InGaAsP/InP buried‐ heterostructure lasers. These lasers have a novel, deeply etched rectangular mesa that results in reduced current leakage. Both single‐stripe lasers and Y‐junction‐coupled multiple‐stripe laser arrays have been demonstrated. The single‐stripe lasers have 12 mA cw threshold currents, differential quantum efficiencies of 32%–34% per facet, and smooth single‐lobe far‐field patterns. The multiple‐stripe arrays lase in‐phase with strong phase coherence.

Concurrent fabrication of InGaAsP/InP buried‐heterostructure laser stripes and mirrors has been demonstrated by the use of dry etching and mass transport. In comparison to previous processes in which the laser stripes and mirrors are fabricated separately, this process offers the advantages of simplicity, built‐in alignment, and improved control of device dimensions. Lasers with a cylindrical and a flat end mirror have threshold currents as low as 22 mA and differential quantum efficiencies as high as 24% per facet. Beam divergences as narrow as 13° are obtained for the cylindrical mirrors.

Low‐loss GaInAsP buried‐heterostructure waveguide branches and bends have been demonstrated using a novel etch and liquid phase epitaxial regrowth technique. Branching losses as low as 0.4 dB at 1.3‐μm wavelength for a 1° branch have been achieved. The measured waveguide propagation loss is ≤1.5 cm−1.

Solid-phase epitaxial growth (SPEG) of silicon was investigated by a tracer technique using radioactive 31Si formed by neutron activation in a nuclear reactor. After depositing Pd and Si onto activated single-crystal silicon substrates, Pd2Si was formed with about equal amounts of radioactive and nonradioactive Si during heating at 400 °C for 5 min. After an 1-sec annealing stage (450-->500 °C in 1 h) this silicide layer, which moves to the top of the sample during SPEG, is etched off with aqua regia. From the absence of radioactive 31Si in the etch, it is concluded that SPEG takes place by a dissociation mechanism rather than by diffusion.

Coherent operation of a monolithic linear array of InGaAsP buried‐heterostructure lasers operating at λ=1.3 μm has been acheived by means of a spatial filter in an external cavity. An array of mass‐transported InP microlenses was used to collimate the beams of the individual laser elements and couple the laser array output to the external cavity. The coherent array output exhibited a narrow (3.2 mrad), three‐lobe far‐field pattern with ∼65% of the energy concentrated in the central peak.