This PDF file contains the front matter associated with SPIE Proceedings Volume 10381, including the Title Page, Copyright information, Table of Contents, and Conference Committee listing.

Al₂O₃ has been an attractive gate dielectric for GaN power devices owing to its large conduction band offset with GaN (~2.13eV), relatively high dielectric constant (~9.0) and high breakdown electric field (~10 MV/cm). Due to exceptional control over film uniformity and deposition rate, atomic layer deposition (ALD) has been widely used for Al₂O₃ deposition. The major obstacle to ALD Al₂O₃ on GaN is its high interface-state density (Dit) caused by incomplete chemical bonds, native oxide layer and impurities at the Al2O3/GaN interface. Therefore, an appropriate surface pretreatment prior to deposition is essential for obtaining high-quality interface. In this study, we investigated the effect of TMA, H₂O and Ar/N₂ plasma pretreatment on D_it and border traps (N_bt). 5 cycles of TMA purge, 5 cycles of H₂O purge and Ar/N₂ plasma pretreatment were conducted on GaN prior to deposition of ALD Al₂O₃. Al₂O₃/GaN metaloxide-semiconductor capacitors (MOSCAPs) were fabricated for the characterization of D_it and N_bt using UV-assisted capacitance-voltage (C-V) technique. The results show that TMA and H₂O pretreatment had trivial effects on interface engineering whereas Ar/N₂ plasma pretreatment slightly reduced D^it and significantly reduced N_bt.

Power electronics is based on the conversion and conditioning of electric power in its different forms. The need for higher operating voltages, temperatures and switching speeds have necessitated for the use of semiconductor materials more superior to Silicon for power electronics purposes. Wide bandgap (WBG) materials like SiC, GaN and Diamond have been known to demonstrate better material properties as compared to Silicon, like higher operating temperatures, higher breakdown voltages and reduced thermal and electrical resistances which make them ideal for high power electronic devices. This paper analyzes the thermal and electrical performance of WBG power MOSFETs, in particular the Vertical Double-diffused MOSFET (VDMOSFET) structure, modeled in the commercial simulation software COMSOL Multiphysics. VDMOSFETs are ideal for high power electronic applications owing to their higher voltage blocking capabilities as compared to the conventional lateral MOSFET structure. COMSOL uses Finite Element/Volume Analysis methods to approximate solutions to differential equations involved with complex geometries and physics. The 3D model investigated in COMSOL for this paper solved for thermal and electrical variables for VDMOSFETs using SiC and GaN as their semiconductor material. Only a quarter of the 3D VDMOSFET structure was modeled for faster computational speed as the structure itself is symmetric about two vertical planes. The temperature profiles and current densities of each WBG material VDMOSFET were analyzed for different operating voltages. These profiles were compared with a Si VDMOSFET model to determine relative similarities and differences between each material.

In this report, we present on a research result of the microstructural and optical properties of ZnO/CuO multilayered films. Three types of multilayer ZnO/CuO stacks were prepared by pulsed laser deposition (PLD) on amorphous SiO2/Si substrates, and then annealed at 500oC for 30 min to improve crystallinity. TEM and XRD analysis of the thin films revealed the formation of multiple crystallographic defects and modification of the dominant growth plane. Consequently, near-band-edge emission in ZnO can be controlled through the number of CuO layers. The detailed microstructure and electro optical properties of multilayered ZnO/CuO thin films will be discussed.

A highly efficient high step–up dc–dc converter is the major requirement in the integration of low voltage renewable energy sources, such as photovoltaic panel module and fuel cell stacks, with a load or utility. This paper presents the development of an efficient dc–dc single–ended primary–inductor converter (SEPIC) for high step–up applications. Three SEPIC converters are designed and studied using different combinations of power devices: a combination based on all Si power devices using a Si–MOSFET and a Si–diode and termed as Si/Si, a combination based on a hybrid of Si and SiC power devices using the Si–MOSFET and a SiC–Schottky diode and termed as Si/SiC, and a combination based on all SiC power devices using a SiC–MOSFET and the SiC–Schottky diode and termed as SiC/SiC. The switching behavior of the Si–MOSFET and SiC–MOSFET is characterized and analyzed within the different combinations at the converter level. The effect of the diode type on the converter’s overall performance is also discussed. The switching energy losses, total power losses, and the overall performance efficiency of the converters are measured and reported under different switching frequencies. Furthermore, the potential of the designed converters to operate efficiently at a wide range of input voltages and output powers is studied. The analysis and results show an outstanding performance efficiency of the designed SiC/SiC based converter under a wide range of operating conditions.

We are investigating conductive gallium nitride films grown on c-plane sapphire for use in a new area of application, high-power optoelectronics. It was found that optically-induced damage in gallium nitride-based transparent conductive thin films occurs at incident laser intensities significantly greater than in conventional metal-oxide based thin films. Furthermore, damage in gallium nitride epi-layers displays a unique morphology consisting of discrete, faceted pits which appear to initiate within fast-grown layers when exposed to high intensity near-infrared laser irradiation. We developed an integrated laser damage system with in-situ diagnostics to probe this damage mode and conducted damage tests of aluminum nitride and gallium nitride/aluminum nitride samples grown under various conditions. Through in-depth analyses using optical microscopy and results from high-throughput damage tests, this paper elucidates some of the prevailing damage processes and design considerations for gallium nitride transparent conductive films important for emerging high-power laser applications.

In this work, a study of two different types of current aperture vertical electron transistor (CAVET) with ion-implanted blocking layer are presented. The device fabrication and performance limitation of a CAVET with a dielectric gate is discussed, and the breakdown limiting structure is evaluated using on-wafer test structures. The gate dielectric limited the device breakdown to 50V, while the blocking layer was able to withstand over 400V. To improve the device performance, an alternative CAVET structure with a p-GaN gate instead of dielectric is designed and realized. The pGaN gated CAVET structure increased the breakdown voltage to over 400V. Measurement of test structures on the wafer showed the breakdown was limited by the blocking layer instead of the gate p-n junction.

Transformer-less inverters are the most efficient approach to utilize renewable energy sources for grid tied applications. In this paper, a grid-tied fuel cell transformer-less single-phase inverter equipped with GaN HEMTs is proposed. The new topology is derived from conventional H5 inverter. The benefits of using GaN HEMTs are to enable the system to switch at high frequency, which will reduce the size, volume and cost of the system. Moreover, inverter control is designed and proposed to supply real power to the grid and to work as DSTATCOM to mitigate any voltage sag and compensate reactive power in the system. A comparison of the performance of the proposed inverter with Si IGBT and GaN HEMTs was presented to analyze the benefits of using WBG devices. The switching strategy of the new topology creates a new current path which reduces the conduction losses significantly. The analysis of the proposed system was carried out using MATLAB/SIMULINK and PSIM and the results show that the proposed controller improves voltage stability, power quality, mitigates voltage sag and compensates reactive power. Accordingly, the results prove the effectiveness of the system for grid-tied applications.

A very simple and inexpensive method for growing β-Ga₂O₃ films by heating GaAs wafers at high temperature in a furnace was found to contribute to large-area, high-quality β-Ga₂O₃ nanoscale thin films as well as nanowires depending on the growth conditions. We present the material characterization results including the optical band gap, Schottky barrier height with metal (gold), field ionization and photoconductance of β-Ga₂O₃ film and nanowires.

In this paper, simulation and performance comparison of Si and SiC based interleaved boost converter is presented. Wide bandgap devices such as silicon carbide and gallium nitride are desirable and recommended in high-power applications because of their capability of operating under high temperature, high switching frequency, and high voltage with reduced switching losses. The main advantage of using SiC materials is the ability to raise the switching frequency which will reduce the size. However, their cost is high compared to Si. In this paper, 60V input voltage is used to get 120V output voltage under 100 KHz switching frequency and 0.5 duty cycle. With the help of LTSpice software, an efficiency comparison between silicon and silicon carbide by considering interleaved boost converter are simulated and studied.

Implementation of transformerless inverters in PV grid-tied system offer great benefits such as high efficiency, light weight, low cost, etc. Most of the proposed transformerless inverters in literature are verified for only real power application. Currently, international standards such as VDE-AR-N 4105 has demanded that PV grid-tied inverters should have the ability of controlling a specific amount of reactive power. Generation of reactive power cannot be accomplished in single phase transformerless inverter topologies because the existing modulation techniques are not adopted for a freewheeling path in the negative power region. This paper enhances a previous high efficiency proposed H6 trnasformerless inverter with SiC MOSFETs and demonstrates new operating modes for the generation of reactive power. A proposed pulse width modulation (PWM) technique is applied to achieve bidirectional current flow through freewheeling state. A comparison of the proposed H6 transformerless inverter using SiC MOSFETs and Si MOSFTEs is presented in terms of power losses and efficiency. The results show that reactive power control is attained without adding any additional active devices or modification to the inverter structure. Also, the proposed modulation maintains a constant common mode voltage (CM) during every operating mode and has low leakage current. The performance of the proposed system verifies its effectiveness in the next generation PV system.

A rigorous analysis of two-dimensional segmented waveguide (2D-SWG) crossing using evolutionary algorithms in conjunction with the two-dimensional finite element method (2D-FEM) is presented. The power transmission and crosstalk of the waveguide crossings are calculated, optimized and compared with other designs in the literature. The optimized crossing has been successfully and efficient designed using evolutionary algorithms based on genetic algorithm (GA). Power transmissions above 90 % and crosstalk below 40 dB over a broadband interval of wavelength have been obtained with the evolutionary algorithm.

Gallium nitride (GaN) based transistors have been of interest to power electronics community because of their high breakdown voltage, high sheet carrier density, and the high saturation velocity of GaN. The low switching losses of GaN enable high-frequency operation which reduces bulky passive components with negligible change in efficiency [1,2]. The most established GaN electronic devices are fabricated on the Ga-polar orientation of GaN. Recently, N-polar GaN based devices are being explored for high frequency applications due to their advantages over Ga-face, such as lower contact resistance since the 2DEG is contacted through a lower bandgap material and better electron confinement due to natural back-barrier provided by the charge inducing barrier [3]. In this work, the first N-polar GaN current aperture vertical electron transistor is presented. The samples were grown by metal-organic chemical vapor deposition on c-plane Sapphire substrate. Mg ions were implanted at 80keV (dose: 1×〖10〗^15 〖cm〗^(-2)) into the top GaN layer, everywhere except the current aperture to form the current blocking layer. A 7 A^0 AlN to reduce alloy scattering followed by 150nm UID N-polar GaN as channel were regrown on top of the implanted structure. The 2DEG density and the mobility of the as-grown sample, determined using Hall measurement, were 1.1×〖10〗^13 〖cm〗^(-2) and 1800 〖cm〗^2/(V-S) , respectively. The CAVET showed excellent device modulation and a maximum current of 2 KA〖cm〗^(-2) at V_G=2V. The maximum transconductance per mm of source was 140 mS. The device had a very large pinch-off voltage of -14V as calculated due to the presence of high charge density in the channel. [1] S. Chowdhury et al 2013 Semicond. Sci. Technol. 28 074014 [2] J. Millán, et al 2014 IEEE Transactions on Power Electronics, 29, 2155 [3] Uttam Singisettiet al 2013 IOP Semicond. Sci. Technol. 28 074006

This paper discusses a proposed DC-DC switched capacitor converter for low voltage electronic products. The proposed converter is a two-level power switched capacitor (PSC) which is a boost converter. The suitability to convert a voltage into four times higher than its input is one of the converter’s objectives. Because of the proposed two-level PSC consist of eight switches and five capacitors, it occupies a small area of the electronic products. The eight switches were selected to be GaN transistors to maintain the efficiency at high rated power or high temperatures. The LTSpice simulator was used to test the proposed model. Since the design contains semiconductor elements such (GaN transistor), then 10% error is a reasonable variance between the mathematical and simulation results.

This paper presents a high-performance dc–dc flyback converter design based on wide bandgap (WBG) semiconductor devices for photovoltaic (PV) applications. Two different power devices, a gallium nitride (GaN)-transistor and a silicon (Si)-MOSFET, are implemented individually in the flyback converter to examine their impact on converter performance. The total power loss of the converter with different power devices is analyzed for various switching frequencies. Converter efficiency is evaluated at different switching frequencies, input voltages, and output power levels. The results reveal that the converter with the GaN-transistor has lower total power loss and better efficiency compared to the converter with the conventional Si-MOSFET.

This paper presents a positive output cascaded boost converter design based on wide bandgap power devices for photovoltaic (PV) applications. The objective is to enhance the converter’s performance and efficiency. The converter with SiC MOSFET devices is discussed and compared to a conventional cascaded boost converter based on Silicon (Si) devices. A 205 W cascaded boost converter with an input voltage of 26.6 V and an output voltage of 400 V is simulated to examine the switching behavior and energy loss of each power device. Converter performance with these two power devices is analyzed in terms of total power loss and efficiency at high switching frequencies and loading conditions. SiC power devices in the cascaded converter set-up perform better with minimized switching loss under a wide range of switching frequency conditions. The results show that the cascaded converter with SiC devices significantly reduces total power loss and improves the overall efficiency.

Uncooled infrared detectors are utilized in various radiometric devices and cameras because of their low cost, light weight and performance. A pyroelectric detector is a class of uncooled infrared detector whose polarization changes with change in temperature. Infrared radiation from objects falls on top of the sensing layer of the pyroelectric detector and the absorbed radiation causes the temperature of the sensing layer to change. This work describes the deposition and characterization of Al_xN_y thin films for using them as pyroelectric detector’s sensing material. To test the sensitivity of infrared detection or pyroelectric effect of Al_xN_y thin films, capacitors of various sizes were fabricated. The diameter of the electrodes for capacitor used during testing of the device was 1100 μm while the distances between these two electrodes was 1100 μm. On a 3-inch diameter cleaned silicon wafer, 100 nm thick Al_xN_y thin films were deposited by radio frequency (RF) sputtering from an Al target in Ar: N₂ environment. On top of this, a 100-nm thick Au layer was deposited and lifted off by using conventional photo lithography to form the electrodes of capacitors. All the layers were deposited by RF sputtering at room temperature. The thin film samples were annealed at 700 °C in N₂ environment for 10 minutes. X-ray diffraction showed the films are poly-crystalline with peaks in (100), (002) and (101) directions. When the temperature varied between 303 K to 353 K, the pyroelectric coefficient was increased from 8.60 × 10^-9 C/m²K to 3.76 × 10^-8C/m²K with a room temperature pyroelectric coefficient value of 8.60×10^-9C/m²K. The non-annealed films were found to be transparent between the wavelengths of 600 nm to 3000 nm. The refraction coefficient was found to be varied between 2.0 and 2.2 while the extinction coefficient was found to be zero. The optical bandgap determined using Tauc’s equation was 1.65 eV.