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High quality germanium doped β-Ga2O3 epitaxial film was grown by PMBE technique and fabricated into a vertical type Schottky photodiode with a Pt/nGa2O3/n+Ga2O3(010) structure. The photodiode exhibited excellent rectifying characteristics with a turn on voltage ~ 1V and near zero bias leakage current ~ 100 fA. The photoresponse measurement showed a true solar blind sensitivity with cutoff wavelength ~260 nm and an out of band rejection ratio of ~104. A maximum responsivity of 0.09 A/W at 230 nm was measured at zero bias, corresponding to an external quantum efficiency of ~52 %. The time response of the photovoltaic diode is in the millisecond range and has no long-time decay component which is very common in the MSM photoconductive wide bandgap devices. The photodiode performance remains stable up to 300°C, suggesting its potential use for high temperature applications.

In this work, the use of manufacturing metrology across the supply chain to improve crystalline silicon (c-Si) photovoltaic (PV) module reliability and durability is addressed. Additionally, an overview and summary of a recent extensive literature survey of relevant measurement techniques aimed at reducing or eliminating the probability of field failures is presented. An assessment of potential gaps is also given, wherein the PV community could benefit from new research and demonstration efforts. This review is divided into three primary areas representing different parts of the c-Si PV supply chain: (1) feedstock production, crystallization and wafering; (2) cell manufacturing; and (3) module manufacturing.

High quality w-MgxZn1-xO thin films were grown epitaxially on c-plane sapphire substrates by plasma-assisted Molecular Beam Epitaxy. ZnO thin films with high crystalline quality, low defect and dislocation densities, and subnanometer surface roughness were achieved by applying a low temperature nucleation layer. By tuning Mg/Zn flux ratio, wurtzite MgxZn1-xO thin films with Mg composition as high as x=0.46 were obtained without phase segregation. Metal- Semiconductor-Metal (MSM) photoconductive and Schottky barrier devices with interdigitated electrode geometry and active surface area of 1 mm2 were fabricated and characterized. Resultant devices showed ~100 A/W peak responsivity at wavelength of ~260nm. We also report on cubic rock salt c-MgxZn1-xO thin films, following a non-traditional approach on MgO substrates, to demonstrate solar-blind photoresponse in MSM photodetectors, realizing a peak responsivity of 460 A/W (@ 250 nm) and 12.6 mA/W (@ 240nm) for mixed phase and single crystal films, respectively. A specific focus of the work is on identifying the impact of various growth parameters on the performance of the c- MgZnO detectors.

In an effort to engineer photonic crystal slab (PCS) devices that operate within a single slab-mode regime, the effect of increased cladding index was studied using FDTD simulation. It is known that while increased cladding index forces the light-cone to constrict in frequency, the single mode condition eases allowing for the use of thicker slabs that remain single-mode. This study shows that the behavior of the photonic band gap is similar to that of the light-cone, sweeping lower in frequency, and even widening in some cases, as cladding index increases. Band gap behavior for both even and odd polarizations over thicknesses from d/a = 0.2 to 0.6 and cladding indices from 1 to 2.5 were studied in efforts to design a single-mode, polarization insensitive, complete band gap. When graphically overlaid, the light-cone, single-mode condition, and transmission spectra represent an enabling reference for the design of realizable structures. For device applications where modal dispersion is detrimental or single mode operation is necessary, a paradigm shift away from air-bridge devices is shown to be essential as single-mode structures of this type demand slab thicknesses far too thin for adequate band gap engineering.

Using finite difference time domain simulations and e-beam assisted lithography we designed and fabricated high transmission transparent contacts for UV nitride devices which consist in perpendicular sets of parallel aluminum lines with a period as low as 260 nm. Transmittance values as high as 100% were predicted for aluminum meshes with the optimized periods, metal line widths and thicknesses. Simulations were compared with optical transmittance measurements. The critical parameters -such as grain size, edge roughness and mesh coating- were determined. The large aluminum grain was decreased by performing a cold aluminum deposition. The aluminum oxide layer over the aluminum mesh was found to reduce the mesh transmittance. Several alternatives were studied to overcome this issue such as coating the mesh with a thin gold or silicon dioxide layer. While the second option appeared promising the addition of the gold layer required much more improvement.

Using e-beam lithography on a single layer of polymethylmethacrylate (PMMA) we designed a relatively thick subwavelength aluminum mesh on top of sapphire. The 100 nm thick mesh consisted of two perpendicularly oriented sets of 100 nm wide parallel metal lines with a center to center distance as low as 260 nm. Due to the large proximity effect during e-beam exposure and the small spacing between metallic lines the use of an adhesion promoting layer appeared necessary to avoid premature peeling of the photoresist. Using a monoatomic layer of hexamethyldisilazane (HMDS) as an adhesion promoter between the sapphire and the PMMA, a 500 nm thick photoresist layer could be exposed and developed with excellent control over the features sizes. Line spacing distances from 500 nm down to 160 nm were achieved. An oxide plasma etch was found to be necessary for metal adhesion during the lift-off process. Due to the small spacing between the aluminum lines, use of a bi-layer photoresist technique to achieve undercut was not possible. Thermal evaporation of aluminum was performed and e-beam evaporation didn't help smoothing the metal surface. An additional ultrasonic bath in acetone was found necessary to ease the lift-off process.

A complete photonic band gap (PBG) in photonic crystal slab (PCS) devices is desirable for various applications, and a realizable device of this kind demands minimal transmittance in-plane as well as out of plane. While in the past much work has considered this problem, none have held transverse confinement as a prime factor. In order to achieve our goal, square and triangular hole shapes are considered. Looking at sharp featured shapes as well as their fabrication realizable rounded counterparts and an even more rudimentary triangular cluster of circles, we look to break the crystalmode symmetries for TM photonic bands and, therefore, open a complete band gap between the 1st and 2nd bands for both TE and TM light. TE/TM gap overlap is optimized for single-slab-mode operation, via the effective index method, for hole size, hole orientation, and slab thickness - all as functions of the lattice constant, a , and operational wavelength, λ. It is found that rounded triangular holes and tri-clustered circular holes of size 0.88 a and thickness d/ λ = 0.112 show identical photonic behavior that provides an optimized gap overlap of 0.0496 (ω a/2 π c = a/ λ) with a 12.81% gap figure of merit (Δω / ω 0 ).

Using 2D finite element modeling with the ability to solve the current continuity equations, carrier energy transport equation, Schrodinger and Poisson equations self-consistently, as well as the scalar wave equation for waveguiding devices, we have investigated the possible improvements of the device efficiencies by introducing transparent p-type contacts and multiple quantum shells (MQSs) in GaN / In 0.14 Ga 0.86 N / GaN / p-AlGaN / p-GaN core/multishell nanowires (CMS NWs). The addition of a transparent p-type current spreading contact was found to promote more uniform current injection into the CMS NWs, thus increasing the current injection efficiency. Despite the inclusion of a transparent ptype contact, the current density remained non-uniform and weighted towards the n-contact side of the NW. This asymmetry in the current density was found to be more important for higher injection current whereas it becomes much more uniform with decreasing injection current. Light generation with the transparent contact was found to become more uniformly distributed along the CMS NW, leading to more even light generation within the device in comparison to NWs without transparent p-type contacts. The replacement of single quantum shells (SQS) by MQSs in the active region of the nitride CMS NW-as has been used for conventional InGaN high brightness LEDs (HB-LEDs)-was found to be advantageous up to three quantum shells, increasing light generation from 80.47 to 94.04 W/m under a 4V bias.

Applications for photonic integrated circuit technologies based on the conditional Faraday Effect with electron spins in quantum dots are discussed. The interaction of light with the quantum confined electrons leads to a rotation of the light polarization. Design considerations for polarization multiplexing systems and plasmon resonance sensors based on polarization rotation are presented. Calculations for light of wavelengths λ=1.3 μm and λ=1.55 μm show devices with active regions of a few hundred microns are possible using InAs/GaAs quantum dots. The advantages of spin-based devices are also discussed.

A comprehensive theoretical analysis of the cavity quantum electrodynamics (QED) in single-photon Mach-Zehnder Interferometer (SMZI) based switches and single quantum gates that are intended for the processing of quantum information encoded in the polarization of single photons inside integrated photonic crystal (PC) quantum networks is presented. These devices rely on manipulating the geometrical phase of single photons by means of the Single-Photon Faraday Effect (SPFE), which can be described in terms of a detuned single mode quantum field strongly interacting with a two-level system or quantum dot (QD) inside nanocavities. The feasibility of such devices depends on the ability for the field in each arm of the interferometer to couple in their respective nanocavities, successfully interact with the quantum dot, and when the appropriate phase is accumulated couple out; all these steps being performed with minimum phase error and losses. Using the Jaynes-Cummings model, the cavity dynamics is studied for various detuning energies and coupling energies, and it is shown that the design of these devices can achieve low phase error and robustness against fabrication errors.

GaAs-based PIN detectors with mesa sizes 1, 2.5, 5, 7.5 and 10 mm were fabricated and characterized for alpha particle response using a Po-210 alpha source. By decoupling the neutron conversion process of a proximity moderator, we were able to directly probe the alpha response characteristics of the PIN detectors as a function of device area. Dark current levels in the PIN detectors ranged from 6.1 to 9.5 pA at zero bias. The dark current values were higher for larger devices and a linear relationship between mesa size and dark current was observed. The PIN detectors were found to have a strong alpha response of up to 5 nA/mm 2 with a linear relation between the response current and mesa area. The measured responsivity of the detectors was 0.014 A/W. The average device efficiency was determined to be 31.5%. Using the measured alpha response properties of the GaAs PIN diodes one is able to select the optimal device area for a given moderator and application specific neutron flux.

Single quantum dots (QDs), based on the InAs/GaAs material system have been characterized by micro-photoluminescence (μPL). The self-organized quantum dots studied are fabricated by the Stransky-Krastanov method, taking advantage of the strain caused by the lattice mismatch between InAs and GaAs. Well-defined narrow excitonic features from individual QDs are monitored in the μPL spectra, upon single or dual tunable laser excitation. The charge state of the quantum dot is revealed from these excitonic lines in the μPL spectra. However, by tuning the laser excitation energy, it is demonstrated that the charge state of the dot can be altered: The distribution of neutral and charged excitons is demonstrated to be extremely sensitive on the laser energy. In addition, with an additional infrared laser, striking changes are induced in the μPL spectra. The results achieved demonstrate the existence of two well-defined excitation energy regions for the main laser, in which the presence of the infrared laser will decrease or increase, respectively, the integrated dot μPL intensity. For excitation above the critical threshold energy of the main laser, the addition of the infrared laser will induce a considerable increase, by up to a factor 5, in the QD emission intensity. At laser excitation below the threshold energy, on the other hand, the QD emission intensity will decrease. This fact is due to reduced carrier capture efficiency into the dot as determined by the internal electric field driven carrier transport. In order to get further insight into the carrier capture process due to the electric field in the vicinity of the QD, the dots have also been subjected to an external electric field In most optical experiments with QDs, electrically injected or photoexcited carriers are primarily created somewhere in the sample outside the QDs, e.g. in the barriers or in the wetting layer. Consequently, excited carriers undergo a transport in the wetting layer and/or barriers prior to the capture into the QDs. This circumstance highlights the crucial role of the carrier transport and capture processes into the dot for the performance and operation of the dot based devices such as QD lasers, QD infrared detectors and QD memory devices. This transport effect on the optical response of the quantum dots has been investigated by subjecting the carriers to an external electric field in μPL measurements. This external field is formed by application of a lateral field between two top contacts. It is demonstrated that the QD PL signal intensity could be increased several times (>5 times) by optimizing the magnitude of this external field.