Sharif Digital Repository

In this paper, the effect of radial structure on the performance of a linear-lateral GaAs high power photoconductive semiconductor switch (PCSS) is investigated. For this purpose a three-dimensional device modeling is used to model the optically initiated GaAs switch. In this simulation a p-type device with carbon as shallow acceptor is compensated by deep donor EL2 level as a trap level. The PCSS device is designed in a back-triggered, radially symmetric switch structure which extends the blocking voltage by reducing the peak electric field near the electrodes. Device modeling was performed and the effect of different trap concentrations on dark I-V characteristics has been investigated. In... 

This paper has investigated the performance of a linear, 6H-SiC high power photoconductive semiconductor switch. A three-dimensional device modeling with SILVACO ATLAS tools was used to model the optically initiated 6H-SiC switch. The 6H-SiC PCSS device is designed in a rear-illuminated, radial switch structure. The material properties of vanadium compensated 6H-SiC PSCC have been analyzed for breakdown, photocurrent profile such as rise and fall time in terms of their applications as a photoconductive switch at high bias conditions. This structure and also new type of illumination extends the blocking voltage by reducing the peak electric field near electrodes. In this presentation the... 

In this paper characteristics of a linear, 6H-SiC photoconductive semiconductor switch are presented. The vanadium-doped semi-insulated 6H-SiC PCSS device is designed in a back-triggered, radial switch structure. For this purpose, three-dimensional (3D) device modeling tool was used to model and test the optically initiated 6H-SiC switch. Dark I-V characteristic results show that newly proposed rear-illuminated radial switch structure extends the blocking voltage by reducing the peak electric fields near electrodes. Also this radial structure has higher dark resistance as compared to the previous 6H-SiC PCSS experimental results. The ON-state characteristics of vanadium compensated 6H-SiC... 

Fault detection (FD) in power electronic converters is necessary in embedded and safety critical applications to prevent further damage. Fast FD is a mandatory step in order to make a suitable response to a fault in one of the semiconductor devices. The aim of this study is to present a fast yet robust method for fault diagnosis in nonisolated dc-dc converters. FD is based on time and current criteria which observe the slope of the inductor current over the time. It is realized by using a hybrid structure via coordinated operation of two FD subsystems that work in parallel. No additional sensors, which increase system cost and reduce reliability, are required for this detection method. For... 

In this paper, a new zero-voltage-switching high power-factor (PF) rectifier with Line-Modulated Fixed-Off-Time current control is introduced, that off time is a function of the instantaneous line voltage. The auxiliary circuit provides soft switching for all semiconductor devices, without any extra current and voltage stress on the main switches. The proposed converter is bridgeless, and all semiconductor devices are soft switched. In addition, there is no extra stress on the switches. Thus, the conduction and switching losses are reduced and maximum efficiency is achieved. A 250W, with an input ac voltage of 90265 Vrms and an output voltage 400 Vdc, 100 kHz is designed and simulated to... 

A 6-bit passive phase shifter for 2.5- to 3.2-GHz frequency band has been designed and implemented in a standard 0.18- μm CMOS technology. A new switched-network topology has been proposed for implementing the 5.625 ° phase shift step. The insertion loss of the circuit is compensated with an on-chip bidirectional amplifier. The measured return losses of the circuit are better than 8 dB with output 1-dB compression point of +9.5 dBm in the transmit mode and noise figure of 7.1 dB in the receive mode. The fabricated phase shifter demonstrates an average rms phase error of less than 2° over the entire operation bandwidth, which makes it suitable for high-precision applications  

Nanoscale Shielded channel transistors are investigated by solving the two-dimensional Poisson equation self-consistently with ballistic quantum transport equations for first time. We present self-consistent solutions of ultrathin body device structures to investigate the effect of electrically shielded channel region which impose charge controlling in the channel region on the characteristics of nanoscale DG-MOSFET. The simulation method is based on Nonequlibrium Green's Function (NEGF). Starting from a basic structure with a gate length of 10 nm, the effect of gate length variation on the performance of the device has been investigated. © 2007 IEEE  

For the first time, we present self-consistent solution of ultrathin body device structures to investigate the device parameters variation on the characteristics of nanoscale MOSFET. Our two dimensional (2-D) device simulator Is based on Nonequlibrium Green's Function (NEGF) forma lism. Starting from a basic structure (DG-MOSFET) with a gate length of 10 nm, variation of gate length, channel thickness, gate oxide parameters was carried out in connection with the numerical calculation of device characteristics. In this work Quantum transport equations are solved in 2-D by NEGF method in active area of the device to obtain the charge density and Poisson's equation is solved in entire domain of...