This PDF file contains the front matter associated with SPIE Proceedings Volume 9957, including the Title Page, Copyright information, Table of Contents, and Conference Committee listing.

Ultra-high voltage power devices are employed for management of power networks. Si-based semiconductor devices have been developed for such the power devices. Maximum breakdown voltages of Si devices are of the order of kV. When the voltage in the power network was higher than the breakdown voltage of the devices, the devices were connected in series. The series connection introduces high resistance and power loss. To overcome this series resistance problem, it has been suggested that utilization of silicon carbide (SiC) devices. SiC has much higher breakdown electric field than Si, and thus high voltage in the power networks can be managed by SiC device without the series connection. Therefore, development of ultra-high voltage SiC device will decrease resistance and power loss in the power networks. However, there are several difficulties to develop ultra-high voltage SiC devices. One of the difficulties is control of the carrier lifetime. In fact, ultra-high voltage devices are fabricated with bipolar structure, and, in the bipolar devices, the carrier lifetime is highly influential on resistance and power loss. The carrier lifetime is limited by several factors, and one of the most important factors is the surface recombination. Therefore, evaluation and control of the surface recombination is essential to develop ultra-high voltage SiC devices. In this paper, we will report evaluation techniques for the surface recombination of SiC. In addition, dependence of the surface recombination on surface treatments, crystal faces and temperature are shown. The evaluated surface recombination velocities will support development of ultra-high voltage SiC devices.

The influence of hydrogen-defect complexes on the properties of n-type ZnO has been studied in terms of annealing and hydrogen plasma irradiation. Both of carrier concentration and Hall mobility increased after the annealing in Ar atmosphere containing Zn (Zn-annealing). The improved electrical properties indicate that the zinc vacancy (V_Zn) concentration was decreased by the Zn-annealing. While the Zn-annealed sample was not affected by hydrogen plasma irradiation, carrier concentration and Hall mobility of the sample annealed in pure Ar atmosphere were increased by hydrogen plasma irradiation. The simultaneous increases in carrier concentration and Hall mobility indicate that V_Zn, which acts as a compensation acceptor, is passivated by hydrogen. The carrier concentration and Hall mobility after hydrogen plasma irradiation decreased with increasing post-annealing temperature. It was found that V_Zn passivated by hydrogen starts to dissociate at temperatures around 400°C. The activation energy for the dissociation of the V_Zn passivated by hydrogen was estimated to be 2.2 eV.

ZnO an interesting material platform provides broad applications in electronics and photonics. In this talk we will discuss the growth of vertically aligned and core-shell nano-structures. Some optical applications will be discussed.

We report the use of sol-gel method at room ambient to grow nanoscale thin film of Ga₂O₃ on Si surface for both surface passivation and gate dielectric. The admittance measurements were carried out in the frequency range of 20 kHz-1 MHz at room temperature. Voltage dependent profile of interfacial trap density (D_it) was obtained by using low and high frequency capacitance method. The capacitance (C)-voltage (V) analyses show that the structures have a low interfacial trap density (D_it) of 1x10¹² cm^-2eV^-1. The Ga₂O₃ thin film synthesized via sol-gel method directly on devices to function as a gate dielectric film is found to be very effective. We also present our experimental results for a number of gate dielectric and device passivation applications.

With fast growing of the photonics and power electronic systems, the need for high power- high frequency semiconductor devices is sensed tremendously. GaN provides the highest electron saturation velocity, breakdown voltage and operation temperature, and thus combined frequency-power performance among commonly used semiconductors. With achieving the first THz image in just two decades ago, generation and detection of terahertz (THz) radiation is one of the most emerging photonic areas. The industrial needs for compact, economical, high resolution and high power THz imaging and spectroscopy systems are fueling the utilization of GaN for the realizing of the next generation of THz systems. As it is reviewed in this paper, the mentioned characteristics of GaN together with its capabilities of providing high 2-dimentional election densities and large longitudinal-optical phonon of ~90 meV, make it one of the most promising semiconductor materials for the future of the THz generation, detection, mixing, and frequency multiplication. GaN- based devices have shown capabilities of operating in the upper THz frequency band of 5- 12 THz with relatively high photon densities and in room temperature. As a result, THz imaging and spectroscopy systems with high resolutions and depths of penetrations can be realized via utilizing GaN- based devices. In this paper, a comprehensive review on the history and state of the art of the GaN- based electronic devices, including plasma HFETs, NDRs, HDSDs, IMPATTs, QCLs, HEMTs, Gunn diodes and TeraFETs together with their impact on the future of THz imaging and spectroscopy systems is provided.

The Wide band-gap (WBG) materials “such as Silicon Carbide (SiC) and Gallium nitride (GaN)” based power switching devices provide higher performance capabilities compared to Si-based power switching devices. The wide band-gap materials based power switching devices outperform Si-based devices in many performance characteristics such as: low witching loss, low conduction loss, high switching frequencies, and high operation temperature. GaN based switching devices benefit a lot of applications such as: future electric vehicles and solar power inverters. In this paper, a DC-DC Buck converter based on GaN FET for low voltage and high current applications is designed and investigated. The converter is designed for stepping down a voltage of 48V to 12V with high switching frequency. The capability of the GaN FET based buck converter is studied and compared to equivalent SiC MOSFET and Si-based MOSFET buck converters. The analysis of switching losses and efficiency was performed to compare the performance capabilities of GaN FET, SiC MOSFET and Si-based MOSFET. The results showed that the overall switching losses of GaN FET are lower than that of SiC and Si-based power switching devices. Also, the performance capability of GaN devices with higher frequencies is studied. GaN devices with high frequencies will reduce the total size and the cost of the power converter. In Addition, the overall efficiency of the DC-DC Buck converter is higher with the GaN FET switching devices, which make it more suitable for low voltage and high current applications.

Although present imaging devices are mostly silicon-based devices such as CMOS and CCD, these devices are reaching their sensitivity limit due to the band gap of silicon. Amorphous selenium (a-Se) is a promising candidate for high- sensitivity photo imaging devices, because of its low thermal noise, high spatial resolution, as well as adaptability to wide-area deposition. In addition, internal signal amplification is reported on a-Se based photodetectors, which enables a photodetector having effective quantum efficiency over 100 % against visible light. Since a-Se has sensitivity to UV and soft X-rays, the reported internal signal amplification should be applicable to UV and X-ray detection. However, application of the internal signal amplification required high voltage, which caused unexpected breakdown at the contact or thin-film transistor-based signal read-out. For this reason, vacuum devices having electron-beam read-out is proposed. The advantages of vacuum-type devices are vacuum insulation and its extremely low dark current. In this study, we present recent progresses in developing a-Se based photoconductive films and photodetector using nitrogen-doped diamond electron beam source as signal read-out. A novel electrochemical method is used to dope impurities into a-Se, turning the material from weak p-type to n-type. A p-n junction is formed within a-Se photoconductive film, which has increased the sensitivity of a-Se based photodetector. Our result suggests a possibility of high sensitivity photodetector that can potentially break the limit of silicon-based devices.

This paper discusses the use of wide bandgap devices (SiC-MOSFET) in the design of a push-pull inverter which provides inexpensive low power dc-ac inverters. The parameters used were 1200V SiC MOSFET(C2M0040120D) made by power company ROHM. This modeling was created using parameters that were provided from a device datasheet. The spice model is provided by this company to study the effect of adding this component on push-pull inverter ordinary circuit and compared results between SiC MOSFET and silicon MOSFET (IRFP260M). The results focused on Vout and Vmos stability as well as on output power and MOSFET power loss because it is a very crucial aspect on DC-AC inverter design. These results are done using the National Instrument simulation program (Multisim 14). It was found that power loss is better in the 12 and 15 vdc inverter. The Vout in the SIC MOSFET circuit shows more stability in the high current low resistance load in comparison to the Silicon MOSFET circuit and this will improve the overall performance of the circuit.

In this paper, DC-DC multilevel cuk converter using silicon carbide (SiC) Components is presented. Cuk converter gives output voltage with negative polarity. This topology is useful for applications require high gain with limitation on duty cycle. The gain of the design can be enhanced by increasing the number of multiplier level (N). This relation between the gain and the number of levels is the major advantage of this multilevel cuk converter. In the proposed cuk converter, a single SiC MOSFET, 2N-1 SiC schottky diodes, 2N capacitors, 2 inductors, and single input voltage are used to supply a load with negative polarity. 300V input voltage, 50KHz switching frequency, and 75% duty cycle are the main parameters used in the design. The output parameters are 3KW power and -5.7 KV voltage. Because this design can be used in applications which temperature plays a critical role, the relation between increasing temperature and output voltage and power are tested. The design is simulated using LTspice software and the results are discussed.

This paper discusses a DC-DC multilevel boost with wide bandgap components for PV applications. In the PV system, the multilevel boost converter is advisable to be used over the conventional boost converter because of the high ratio conversion. The multilevel boost converter is designed with one inductor, 2N-1 silicon carbide (SiC) schottky diodes, 2N-1 capacitors and one SiC MOSFET where N is the number of levels. Inserting SiC components in the design helps to maintain the temperature effect that could cause a high power loss. Most function of using a multilevel boost converter is to produce a high output voltage without using either a power transformer or a coupled inductor. Achieving a high gain output in the multilevel boost converter depends on the level of the converter and the switching duty cycle. The demonstrated design is a multilevel boost converter supplies from 220 V to rate 2 KW power. The switching frequency is 100 KHz and the output voltage of 4-level is 3.5 KV. Several values of temperatures are applicable to the system and the effect of changing the temperature on efficiency is studied. The developed design is simulated by using a LTspice software and the results are discussed.

The development of Wide band gap (WBG) power devices has been attracted by many commercial companies to be available in the market because of their enormous advantages over the traditional Si power devices. An example of WBG material is SiC, which offers a number of advantages over Si material. For example, SiC has the ability of blocking higher voltages, reducing switching and conduction losses and supports high switching frequency. Consequently, SiC power devices have become the affordable choice for high frequency and power application. The goal of this paper is to study the performance of 4.5 kW, 200 kHz, 600V DC-DC boost converter operating in continuous conduction mode (CCM) for PV applications. The switching behavior and turn on and turn off losses of different switching power devices such as SiC MOSFET, SiC normally ON JFET and Si MOSFET are investigated and analyzed. Moreover, a detailed comparison is provided to show the overall efficiency of the DC-DC boost converter with different switching power devices. It is found that the efficiency of SiC power switching devices are higher than the efficiency of Si-based switching devices due to low switching and conduction losses when operating at high frequencies. According to the result, the performance of SiC switching power devices dominate the conventional Si power devices in terms of low losses, high efficiency and high power density. Accordingly, SiC power switching devices are more appropriate for PV applications where a converter of smaller size with high efficiency, and cost effective is required.

This paper investigates the thermal performance of different wide bandgap (WBG) materials for their applicability as semiconductor material in power electronic devices. In particular, Silicon Carbide (SiC) and Gallium Nitride (GaN) are modeled for this purpose. These WBG materials have been known to show superior intrinsic material properties as compared to Silicon (Si), such as higher carrier mobility, lower electrical and thermal resistance. These unique properties have allowed for them to be used in power devices that can operate at higher voltages, temperatures and switching speeds with higher efficiencies. Digital prototyping of power devices have facilitated inexpensive and flexible methods for faster device development. The commercial simulation software COMSOL Multiphysics was used to simulate a 2-D model of MOSFETs of these WBG materials to observe their thermal performance under different voltage and current operating conditions. COMSOL is a simulation software that can be used to simulate temperature changes due to Joule heating in the case of power MOSFETs. COMSOL uses Finite Element/Volume Analysis methods to solve for variables in complex geometries where multiple material properties and physics are involved. The Semiconductor and Heat Transfer with Solids modules of COMSOL were used to study the thermal performance of the MOSFETs in steady state conditions. The results of the simulations for each of the two WBG materials were compared with that of Silicon to determine relative stability and merit of each material.