This PDF file contains the front matter associated with SPIE Proceedings Volume 6479, including the Title Page, Copyright information, Table of Contents, Introduction (if any) and the Conference Committee listing.

Electrons with the spin polarization vector perpendicular to the magnetization direction are spin analyzed after reflection at a ferromagnetic surface. The spin polarization precesses around the magnetization and simultaneously the angle between spin polarization and magnetization is changed. This spin motion is explained by the existence of a gap in the electronic band structure of the ferromagnet.

There have been several recent experiments involving spin injection and accumulation in mesoscopic metal samples, using lateral spin valve structures. The results have been interesting from the perspectives of both fundamental physics and applications. The resistance change associated with spin accumulation, ▵R, has been predicted to scale inversely with sample volume and this inverse scaling has been observed over ten decades. A value of ▵R = 1 Ohm has been reported, at room temperature, in a thin film Al wire structure with transverse dimensions of roughly 100 nm. High values of ▵R have been observed in samples characterized by electrode interface resistances that vary by 6 decades. Results are discussed within the framework of Johnson-Silsbee theory, and factors that limit inverse scaling are identified. Lateral spin valves with dimensions of tens of nm may be competitive for device applications. Structures with ▵R of order 1 Ohm are superior to CPP spin valves of comparable dimensions. Prospects for improved performance, the plausibility of a lateral spin valve with output levels of 10 Ohms and output impedance of 50 Ohms, and relevance to hard drive read heads and integrated nonvolatile random access memory applications are discussed.

We report on the development of an analytical theory and a method of experimental observation of dynamic properties of magnetic vortices excited in cylindrical ferromagnetic discs magnetostatically coupled into arrays. The theory, based on Thiele's equation of motion and the approximative rigid-vortex model, enables us to determine the eigenfrequencies of the vortices' harmonic oscillation within pairs [J. Shibata et al., Phys. Rev. B 67, 224404 (2003)] and large arrays [J. Shibata and Y. Otani, Phys. Rev. B 70, 012404 (2004)] of the discs, the latter being a proposal to design a new type of artificial crystals with magnonic band structures. Then we briefly describe the basic principles of our time-resolved Kerr microscope and show the capabilities of our method to detect all the features studied theoretically. Finally we present an experimental example of observation of the dynamic evolution of short-pulse magnetic field excitation of a vortex weakly coupled within an array of cylindrical Permalloy discs.

In a crystal without inversion center, when the spin-orbit interaction is taken into account, it has been shown that the evanescent branches inside the forbidden band gap correspond to complex wave vectors. Here, we discuss possible tunneling phenomena associated with complex wave vectors. We demonstrate that in a case where the wave vector has orthogonal real and imaginary components, an almost standard tunneling process can be restored under crude approximations, analoguous to off-normal tunneling through a potential barrier. Any more accurate analysis is an open problem. In one-dimensional tunneling with a complex wave vector, no solution can be calculated under simple hypotheses.

Scanning photocurrent microscopy was used to study carrier transport processes in semiconductor nanowire photodetectors. Under high-level local carrier injection in CdS nanowire devices, spatially non-uniform photocurrent distributions were observed and explained in terms of bipolar transport with spatially separated electrons and holes. The mobility-lifetime product, (μτ)*, for both electrons and holes was determined in intrinsic CdS nanowire photodetectors under high-level injection. (μτ)* was enhanced compared to the bulk values as a result of the carrier spatial separation. Local time-resolved photocurrent measurements supported this interpretation of the enhanced (μτ)*. Global timeresolved photocurrent measurements were used to establish a 10%-90% rise time of ~ 6ns (limited by the instrument response) and a 90%-10% fall time of ~ 20ns for the nanowire photodetectors. A small fraction of the total photocurrent exhibited a long power-law decay attributed to carrier trapping/detrapping processes, and characteristic shallow trap energy of 60meV was extracted. Spatially uniform photocurrent profiles were observed in Si nanowire photodetectors under low-level injection conditions, consistent with unipolar minority carrier transport. Under varying biases, consistent variations in the photocurrent profiles were observed and attributed to the effect of the applied electric fields on drift and diffusion of minority carriers.

Free-Standing Quantum dots (FSQdot), also known as nano-crystals, are semiconductors composed of II-VI, III-V, or IV-VI materials. Ranging in size from 2-10 nanometers in diameter, these FSQdots have size-tunable band gaps. Unlike Qdots produced on semiconductor wafers, FSQdots can be manufactured using scalable colloidal solution chemistry. These FSQdots have high photo-luminescence quantum efficiencies, good thermal and photo-stability, narrow emission line widths (atom-like spectral emission), and are compatible with solution processing. Solution processable FSQdots can be modified using innovative surface functionalization schemes. Once appropriately functionalized, the FSQdots can be incorporated into printable inks and bound to surfaces. These capabilities unlock a realm of possibilities for producing novel commercial electronic products, from unique surface coatings to new display constructions.

For over fifteen years, micro-Channel plate (MCP) optics, later termed "Micro Pore Optics" (MPOs) - have been under development to replace the heavy Wolter Type 1 replicated or foil mirrors currently used in X-ray astronomy. Noting other possible applications, including X-ray Lithography and imaging X-ray fluorescence spectroscopy - and after considerable, sustained investment from the European Space Agency Technology Research Programme (TRP), a reliable manufacturing process has now been established, able to produce high quality, low mass X-ray and UV optics in a variety of formats. Optimisation of the glass preparation and drawing technology, in line process controls and metrology as well as improvements in the fibre stacking processes, core glass etching and plate slumping have all been developed. Channel coating methods have also been developed to enhance the high energy response. All these improvements enable Photonis to offer MPOs with square pores from 10x10 μm up to 100x100 μm, with channel aspect ratios of up to 500:1 in both square and radially packed geometries in various shapes and with focal lengths in the range 10 cm to several metres. Space science projects such as LOBSTER (an X-ray all-sky monitor), the Wide Field Auroral Imager for Kuafu B and the Mercury Imaging X-ray Spectrometer (MIXS) for BepiColombo are likely to benefit from this unique technology. Other applications are, however, under consideration, such as X-ray pulsar- based navigation systems for autonomous terrestrial and space navigation. The potential industrial-commercial market interest in developing these compact X-ray lenses for ground-based applications is the subject of our paper.

Electronic and optical properties of ideal and real quantum dots (QDs) are extensively studied and derived for the recent decade. Strain caused by the differences of the lattice constants of dot and wetting, barrier materials are decisive for both the self-assembly mechanisms and the electro-optical properties. The research is mainly investigated for realizing the strain effects on the optical properties of InAs/GaAs self-assembled QDs embedded in GaAs barrier layer incorporated with the three-dimensional (3D) Schördinger equation and solved by using finite element method (FEM). From 3D QD geometrical profiles establishing by the spatially geometric equations, the confined electron and hole bandstructures on altering sized lens and pyramidal shape-like QDs with numerical calculations and strained heterostructure of the finite element approximations have been proposed. Applying the fast FEM models, it is demonstrated that the correspondence of ground, excited eigenstates, the probability of density function (|Ψ|²) of the confined levels from the single InAs QD to a matrix of nine QDs to obtain the transition energy and coordinated absorption wavelength to be predicted and summarized clearly. Through calculating energy levels within the conduction and valence band edge confinement on the InAs/GaAs heterostructure with FEM to contradistinguish with corrected to optical transitions and linear absorption spectra can be achieved for verifying to being the specific wavelengths from photoluminescence (PL) and photoresponse (PR) measurements for quantum dot infrared photodetector. By fitting the energy differences among the subbands, the geometrical shape and size of QD can be predicted. Inducting the tendency from single QD to the matrix of 9 QDs, the step-wise bands have been obtained being some regularity clearly. And from the transmission electron microscope (TEM) measurement, the dominant sizes of QDs in the really grown wafer remain the consistent with the numerical analyses applied in 3D QD profile that is interpreted using spatially geometric equations.

Novel optoelectronic systems based on ensembles of semiconductor nanocrystals are addressed in this paper. Colloidal semiconductor quantum dots and related quantum-wire structures have been characterized optically; these optical measurements include those made on self-assembled monolayers of DNA molecules terminated on one end with a common substrate and on the other end with TiO₂ quantum dots. The electronic properties of these structures are modeled and compared with experiment. The characterization and application of ensembles of colloidal quantum dots with molecular interconnects are considered. The chemically-directed assembly of ensembles of colloidal quantum dots with biomolecular interconnects is demonstrated with quantum dot densities in excess of 10⁺¹⁷ cm^-3. A number of novel photodetectors have been designed based on the combined use of double-barrier quantum-well injectors, colloidal quantum dots, and conductive polymers. Optoelectronic devices including photodetectors and solar cells based on threedimensional ensembles of quantum dots are considered along with underlying phenomena such as miniband formation and the robustness of minibands to displacements of quantum dots in the ensemble.

In optical fiber evanescent wave sensors, the interaction with the surrounding environment is usually obtained by tapering an optical fiber, which significantly weakens the structure. This paper describes different processes for developing optical fiber probes with gold nanoparticles on the fiber tip including focused ion beam lithography and annealing of continuous gold films by employing plasma arcs, high temperature, or a focused ion beam. Along with the tip based sensors, robust in-line optical fiber sensors were developed by fusing multimode fibers to coreless fibers and forming nanoparticles on the surface of the coreless fibers. The fiber-optic sensors were placed in mediums of different refractive indices to evaluate their chemical sensing capability.

The THz region is of considerable interest with research on both single element detectors and imagers. Results are reported on heterojunction and homojunction detectors using III-V semiconductor materials. Both Nitride and Antimonide based detectors showed broad response frequencies out to 1 THz. Arsenide based detectors have shown a threshold frequency tailorable in the range of 2.3-20 THz. The mechanisms of operation in these detectors will be discussed, and potential advantages and disadvantages of the materials for various frequency ranges will be considered. Among these are the increased control in tailoring the workfunction in antimonides, and increased THz absorption in the nitrides. The usage of surface plasmon effects in surface structures such as gratings to enhance detector response is also considered. The enhanced frequency for a given grating can be determined from the phase-matching condition. For a grating with 4.5 &mgr;m spacing this leads to increased absorption at 14 &mgr;m. Experimental results on the effects of surface plasmons on absorption and reflection will be presented. Designs for improved THz detectors based on these ideas will also be discussed.

In this work, an AlSb-containing Type II InAs/GaSb superlattice, the so-called M-structure, is presented as a candidate for mid and long wavelength infrared detection devices. The effect of inserting an AlSb barrier in the GaSb layer is discussed and predicts many promising properties relevant to practical use. A good agreement between the theoretical calculation based on Empirical Tight Binding Method framework and experimental results is observed, showing the feasibility of the structure and its properties. A band gap engineering method without material stress constraint is proposed.

A spectrally resolving quantum dot photodetector has been designed and fabricated which is able to discriminate wavelengths in the visible region. The device consists of a monolayer of 5.4 nm diameter CdSe nanoparticles that have been sandwiched between two organic layers of Hexanedithiol, all on a highly doped p-type InP substrate. A thin, semitransparent layer of gold deposited on the top of the device made the second contact. The two layers of Hexanedithiol act as tunnel barriers for electrons inside the nanoparticles. Changing the bias voltage across the device, causes specific energy states inside the quantum dot to align with the conduction band edge of the InP. Any excited carriers in these energy levels will tunnel trough the organic barrier and be collected as photocurrent. By changing the wavelength of the incident light, the device shows a wavelength dependent I-V spectrum with jumps in the current at specific voltages. Comparing which peaks in different wavelengths are present, shows that the device has a spectrally dependent response to the incident light.

Epitaxially grown self-assembled InAs/InGaAs/GaAs quantum dots (QDs) are exploited for the development of large-format long-wavelength infrared (LWIR) focal plane arrays (FPAs). The Dot-in-a-Well (DWELL) structures were experimentally shown to absorb both 45° and normal incident light, therefore a reflection grating structure was used to enhance the quantum efficiency. The devices exhibit peak responsivity out to 8.1 microns, with peak detectivity reaching ~ 1 x 10¹⁰ Jones at 77 K. The devices were fabricated into the first long-wavelength 640x512 pixel QDIP imaging FPA, which has produced excellent infrared imagery with noise equivalent temperature difference of 40 mK at 60K operating temperature.

Dualband infrared focal plane arrays (FPA) were developed originally for multi-spectral imaging applications, where their advantages in compactness and band-to-band pixel registration, relative to conventional multispectral imagers, were recognized. As dualband FPA architecture is matured for quantum well and mercury cadmium telluride focal plane arrays, and becomes within the grasp of strained layer superlattice technology, applications in addition to multi-waveband imaging come to mind. In various hyperspectral applications that employ gratings, the different grating orders can sometimes be paired with the wavebands of the dual- (or multi-) waveband FPA, allowing high efficiency hyperspectral imaging over very broad wavelength regions. Exploiting the "third dimension" of FPA detecting layers for dual- and multi-waveband capability proved its usefulness for multi-waveband imaging; this paper will show similar advantages for hyperspectral applications and describe such applications.

The uni-traveling-carrier photodiode (UTC-PD) is a novel photodiode that utilizes only electrons as the active carriers. This unique feature is the key to realize its excellent high-speed and high-output characteristics simultaneously. To date, a record 3-dB bandwidth (f_3dB) of 310 GHz and a very high millimeter (mm)-wave output power of over 17 mW at 120 GHz have been achieved. These superior characteristics are essential for the detection of high-bit-rate optical signal in communications systems and for the generation of high-frequency electro-magnetic waves in measurement and sensing systems. For optical communications, we have realized a photoreceiver operating at up to 160 Gbit/s and an avalanche photodiode with a record f_3dB of 40 GHz. For generating mm-/sub-mm-wave signals, we have developed a compact UTC-PD module with a rectangular waveguide output port for operation at up to 325 GHz. We have also fabricated a quasi-optical module for operation at higher frequencies integrating a UTC-PDs and a planar log-periodic antenna. This module can be operated at up to 1.6 THz with a maximum output-power of 2.6 μW at 1.04 THz. The UTC-PD has been used successfully for several applications, such as mm-wave imaging and photonic local signal supply for radio telescopes, demonstrating its feasibility for high-frequency measurement and sensing systems. As a challenge for future high-sensitivity sensing systems, the possibility of UTC-PD modules operating at a very low temperature of 15 K has also been demonstrated.

Recently we have achieved significant improvements in the performance of LWIR type-II superlattice photodiodes, with discrete devices beginning to demonstrate dynamic impedance-area product (R0A) levels approaching the MCT trend line and quantum efficiency exceeding 30% in devices without anti-reflection coatings. We discuss the key innovations that have led to these improvements, including modified W-structures, band-gap grading, and hybrid superlattices.

We describe the performance of submicron microdisk and photonic crystal lasers fabricated within InGaP/InGaAlP quantum well material. The smallest lasers, with diameters of approximately 600 nm, feature ultra-small mode volumes and exhibit single mode operation at low threshold powers. Their small cavity volumes of approximately 0.03 μm³ for microdisk lasers and 0.01 μm³ for photonic crystal lasers enable them to be used as spectroscopic sources. Here we demonstrate the fabrication and characterization of visible, monolithically fabricated, submicron mode volume lasers.

We report on recent advances in the performance of GaSb-based vertical-external-cavity surface-emitting lasers (VECSELs) emitting at wavelengths around 2.3 μm. Barrier-pumped VECSELs have been fabricated and analysed, which incorporates a diamond intra-cavity heat spreader as an efficient means for heat extraction from the active region. A maximum output power of 1.5 W has been achieved at a heat sink temperature of -20°C and still more than 1 W at 10°C. Two VECSEL structures with different spectral offsets ▵λ between the microcavity resonance and the maximum of the gain spectrum have been examined in particular. The results clearly show that the proper choice of this offset ▵λ is critical for an optimization of the high-power performance of the VECSEL, e.g. maximizing the output power before thermal rollover.

Significant recent advances in the high-temperature, high-power performance of type-II antimonide interband cascade lasers (ICLs) operating in the mid-infrared are reported. A 5-stage ICL with a 12-&mgr;m ridge width and Au electroplating for improved epitaxial-side-up heat sinking operates cw to a maximum temperature of 257 K, where the emission wavelength is 3.7 &mgr;m. A similar device with a ridge width of 22 &mgr;m emits > 260 mW per facet for cw operation at 80 K (λ = 3.4 &mgr;m) and 100 mW at 200 K (λ = 3.6 &mgr;m). Beam qualities for the narrowest ridges approach the diffraction limit. A single-mode output power of 41 mW has been obtained at T = 120 K and λ ≈ 3.44 μm from a 13-&mgr;m-wide ICL patterned with a Ge distributed-feedback grating. The side mode suppression ratio at the maximum power is 23 dB, and the linewidth of 0.1 nm is instrument-limited. An alternate contacting geometry yielded robust single-mode output over a broad range of currents and temperatures, and current tuning of the wavelength by up to 17 nm.

We report on the fabrication of THz quantum cascade lasers (QCLs) based on different optical waveguide configurations and compare the thermal properties of THz devices fabricated with metal-metal optical waveguides based on Au/Au or In/Au wafer bonding. In particular, we show how the careful choice of the metal sequence used for the reactive bonding may lead to a considerable improvement of the device thermal performance. This information was obtained from the analysis of microprobe band-to-band photoluminescence spectra measured on devices operating in continuous wave (cw). The experimental normalized thermal resistances (R_L^*), show that the use of Au/Au wafer bonding optimizes the heat dissipation. An extensive comparison with a set of surface-plasmon based THz QCLs, demonstrate that the use of metal-metal wafer bonding can allow cw operation at progressively higher temperatures. Finally, we present the experimental results obtained on a bound-to-continuum QCLs (2.84 THz) emitting 77 mW peak power at 4K, fabricated from an MBE wafers acquired by a commercial provider.

GaInAsPSb is a new narrow gap semiconductor material, which is suitable for the fabrication of semiconductor light sources for the mid-infrared spectral range. Unique physical properties of the alloy are discussed and its advantages for mid-infrared optoelectronic devices are considered. Liquid phase epitaxy (LPE) growth conditions for GaInAsPSb homogeneous high crystal quality layers lattice-matched onto GaSb substrates were determined. Spectra of photoluminescence (PL) emission were investigated. Homojunction p-i-n light-emitting diodes (LEDs) based on this pentenary alloy were fabricated and electroluminescence (EL) peaking near 4.0 μm at room temperature was observed.

We report the development and application of an artificial hair cell (AHC) flow sensor inspired by biological systems. With optimized design and fabrication process, the AHC is characterized in terms of sensitivity, calibration, and robustness. Especially, an AHC can discern variations of water flow down to 0.1mm/s and survive 55^o deflections. The sensor has been applied to flow field measurements, matching perfectly with analytical and previous experimental results. By employing arrays of such AHC sensors, an artificial lateral line is constructed for biomimetic studies on localizing and tracking hydrodynamic events.

We have used MBE to grow MQW structures on MOVPE GaN/sapphire templates. The MQW devices are intended for high speed intersubband electroabsorption modulator devices operating at 1.55-&mgr;m. The GaN/AlN multiple quantum well material was systematically studied regarding the surface morphology, structural characterization and optical property by atomic force microscopy, X-ray diffraction and Fourier transform infrared spectroscopy, respectively. The intersubband resonance energy was also calculated considering many-body effects in n-type doped structures. The multiple quantum well structure showed superior performance in terms of linewidth when grown on GaN templates as compared on sapphire. GaN quantum well and AlN barriers with a thickness of 3.3 and 4.2 nm respectively resulted in FWHM of the intersubband absorption peak as low as 93 meV at an absorption energy of 700 meV. This is promising for intersubband modulator applications.

Self-assembled InGaN quantum dots are fabricated in a two-flow horizontal MOCVD reactor maintained at the pressure of 200torr. The precursors were trimethyl-gallium (TMG) and trimethyl-indium (TMI) and ammonia (NH₃), and the carrier gas was N₂ and H₂. The optimum condition was deduced to fabricate the InGaN quantum dots. GaN nucleation layer was grown at 500°C with thickness of 25nm, and then 2~3 μm thick GaN buffer-layer was deposited at 1050 °C. InGaN quantum dots were grown on GaN buffer layer. Carrier gas was changed with N₂ instead of H₂ in QD growth. In the growth of InGaN quantum dots, NH₃ was supplied in cyclic periodic interrupted mode with the interval of 5 seconds. The influence of number of periodic interrupted NH3 on the structural and optical properties of InGaN quantum dots was investigated by AFM, FE-SEM and photoluminescence (PL). The InGaN quantum dots are grown by 2 periods growth and have 0.4nm in height and 31nm lateral size. The height of quantum dots was increased with increase of growth periods, and the lateral size was decreased after 3 periods and then increased in 4 periods. The density of InGaN quantum dots with 3 periods and 4 periods was measured to be 1.51×10¹¹/cm² and 8.91×10¹⁰/cm². Density of InGaN quantum dots was decreased after 3 periods, and this is attributed to the coalescence. A strong peak at 362.2 nm (3.41eV) and broad emission peak in 532.9~663.9nm (2.33~1.86eV) were evolved in the photoluminescence measurement using Nd-YAG laser with wavelength of 266nm. Addition emission peak was found in the range 433.7nm~462.2nm (2.85eV~2.68eV) in the samples with 3 periods and 4 periods interruption, and this peak was identified as the InGaN quantum dots with low indium concentration.

The development of wide band gap semiconductors extends their applications in optoelectronics devices to the UV domain. Compact lasers and high sensitivity APD detectors in UV range are currently needed for different applications such as, purification, covert communication and real time detection of airborne pathogens. Until now, the full exploitation of these potential materials has been limited by the lack of suitable GaN substrates. Recently, a novel class of materials has been reported based on BGaN and BAlN, potentially reducing the crystal defect densities by orders of magnitude compared to existing wide band gap heterostructures. Characteristics of these new alloys are similar to those of AlGaN materials with the advantage that these can be lattice matched to AlN and SiC substrates. In addition, these materials offer the possibility of using quaternary BAlGaN alloys at Ultra Violet (UV) wavelengths and hence lead to more degrees of freedom in designing sophisticated device structures. In this paper we describe the MOVPE growth conditions used to incorporate boron in GaN and AlGaN. Detailed characterization and analysis in terms of structural and electrical properties are discussed.

We have developed AlGaN films deposited by plasma assisted molecular beam epitaxy (PA-MBE) that can possess enhanced internal quantum efficiency (> 30%) due to the presence of nanometer scale compositional inhomogeneities (NCI-AlGaN) within a wider bandgap matrix that inhibit nonradiative recombination through the large defect densities (> 10¹⁰cm^-2) in these materials. Time- and temperature-dependent studies of the UV photoluminescence from these NCI AlGaN films as a function of growth conditions have been performed with the goal of optimizing the emission efficiency. Measurements of radiative and nonradiative lifetimes in conjunction with modeling indicate that the NCI AlGaN inherently combines inhibition of nonradiative recombination with reduction of radiative lifetime, providing a potentially higher efficiency UV emitter active region.

Recent progresses in epitaxial growth and fundamental studies on electrical and optical properties of high Al-content AlGaN alloys with Si, Mg, and Zn doping are presented. For Si doped Al_xGa1-_xN, the Si activation energy was determined for x = 0 up to 1, and the resistivity of n-Al_xGa1-_xN was found to increases by one order of magnitude when Al content is increased by ~ 8%. From photoluminescence (PL) studies, three groups of deep impurity transitions were observed, related with deep level acceptors involving cation vacancy and its complexes: (VIII)^3-, (VIII-complex)², and (VIII-complex)^1-, which are electron traps and compensating centers. By optimizing the growth processes to reduce the densities of cation vacancy and its complexes, the n-type conductivity of Al_xGa1-_xN was significantly improved. A record low room temperature n-type resistivity of 0.0075 Ω•cm has been obtained for Al_0.7Ga_0.3N, and n-type conduction in pure AlN has also been achieved. We also review the electrical and optical measurement results of Mgdoped AlGaN and AlN. It was found that the overall material quality and conductivity of Mg-doped AlN are strongly correlated with the PL emission intensity of the nitrogen vacancy (V_N ³⁺) related transition. Improved conductivity was obtained by suppressing the V_N³⁺ related emission line, which was attributed to the reduced hole compensation by V_N³⁺. With the identification of the emission peaks associated with V_N³⁺ hole compensating centers, the p-type conductivity of high Al-content AlGaN alloys was improved by monitoring and suppressing the intensity of the V_N³⁺ related emission lines. P-type conduction in Al_xGa1-_xN (x > 0.7) was confirmed at elevated temperatures (> 700 K). The possibility of using Zn as an alternative p-type dopant was also studied. It was found that contrary to the calculation, the energy level of Zn acceptor in AlN was about 0.74 eV, which is 0.23 eV deeper than Mg level in AlN.

Wide bandgap III-Nitride semiconductors are a promising material system for the development of ultraviolet avalanche photodiodes (APDs) that could be a viable alternative to photomultiplier tubes. In this paper, we report the epitaxial growth and physical properties of device quality GaN layers on high quality AlN templates for the first backilluminated GaN p-i-n APD structures on transparent sapphire substrates. The 25 μm x 25 μm device characteristics were measured, and compared with the same devices grown on GaN templates, under low bias and linear mode avalanche operation where they exhibited gains near 1500 after undergoing avalanche breakdown. The breakdown electric field in GaN was determined to be 2.73 MV/cm. The hole impact ionization coefficients were shown to be greater than those of electrons. These APDs were also successfully operated under Geiger mode.

We report on the comparison of optical, structural, and electrical properties of SiO₂ using plasma-enhanced chemical vapor deposition and ion-beam sputtering deposition. High-quality, low-temperature deposition of SiO₂ by ion-beam sputtering deposition is shown to have lower absorption, smoother and more densely packed films, a lower amount of fixed oxide charges, and a lower trapped-interface density than SiO₂ by plasma-enhanced chemical vapor deposition. This high-quality SiO₂ is then demonstrated as an excellent electrical and mechanical surface passivation layer on Type-II InAs/GaSb photodetectors. The device performance improved by at least two orders of magnitude in surface resistivity, trap density, and zero-bias resistance-area product. The passivation layer also allows the device the ability to withstand the reflow and curing of underfill epoxy.

We demonstrate an extremely efficient chemical vapour deposition synthesis of single-walled carbon nanotubes where the activity and lifetime of the catalysts are enhanced by controlling the ambient of the CVD furnace, a growth mode we call "Super Growth" [1]. The enhanced catalytic activity of super growth results in massive growth of super-dense and vertically-aligned single-walled nanotubes forests with heights up to 2.5 millimeters. In addition, these SWNT forests were easily separated from the catalysts, producing the most pure SWNT material (over 99.98%) ever made, through an all-dry process without any purification. Moreover, patterned highly organized intrinsic single-walled nanotube structures were successfully fabricated. Super Growth simultaneously addresses many critical problems such as scalability, purity, and cost, and opens up innumerable opportunities ranging from fundamental research to real applications.

We present a description of surface plasmon resonance (SPR) with quantum dynamical simulations based on the path integral method. SPR represents the excitation of surface plasmons (SPs), i.e., collective oscillations of conduction electrons in a metal film, usually created by the plane-polarized visible light. In the classical description, the momentum matching between incident photons and SPs allows the energy of the incident photons to be absorbed into exciting SPs and to form evanescent waves on the metallic thin film surface. While SPR has been understood through classical approaches using Maxwell's equations, extremely small nanoparticles coupled with SPs induces electromagnetic field enhancement often called localized SPR (LSPR) that is classically not well understood. Use of such nanoparticles smaller than a few nanometers in size has made it imperative to consider quantum effects such as quantum size effect. We present a hybridized model to describe SPR/LSPR using quantum states that interact with a dissipative medium according to size-dependent absorption spectra of nanoparticles.