Ali Salih

An industrial process for 650V rated GaN-on-Si power devices using in-situ SiN as a gate dielectric

This paper reports on an industrial DHEMT process for 650V rated GaN-on-Si power devices. The MISHEMT transistors use an in-situ MOCVD grown SiN as surface passivation and gate dielectric. Excellent off-state leakage, on-state conduction and low device capacitance and dynamic Ron is obtained. Initial assessment of the intrinsic reliability data on the in-situ SiN is provided.

On the impact of carbon-doping on the dynamic Ron and off-state leakage current of 650V GaN power devices

A strong positive correlation between dynamic Ron and the ionization of buffer traps by injection of electrons from the Si substrate is presented. By exploring different Carbon doping profiles in the epi layers, the substrate buffer leakage is substantially reduced, which in turns results in lower dynamic Ron. The traps in the epi structure are characterized by different electrical techniques such as drain current transient, on-the-fly trapping and ramped back-gating experiments.

Impact of buffer leakage on intrinsic reliability of 650V AlGaN/GaN HEMTs

The role of buffer traps (identified as CN acceptors through current DLTS) in the off-state leakage and dynamic Ron of 650V rated GaN-on-Si power devices is investigated. The dynamic Ron is strongly voltage-dependent, due to the interplay between the dynamic properties of the CN traps and the presence of space-charge limited current components. This results in a complete suppression of dyn Ron degradation under HTRB conditions between 420V and 850V.

Process & design impact on BV DSS stability of a shielded gate trench power MOSFET

This paper discusses the breakdown voltage (BVDSS) characteristics of an n-channel charge balanced shielded gate trench power MOSFET. The study emphasizes on elements that affect the BVDSS stability of such devices to gain good control on design and process/device parameters in order to produce a robust product. Breakdown voltage (BVDSS) walk-in or walk-out can be observed when certain process (e.g., epi doping concentration) and design layout (e.g., termination) conditions are not in coherence.

IGBT for high performance induction heating applications

Power Semiconductor IGBT has been the enabling technology for induction heating power inverters. In this paper key IGBT device design techniques and their attributes will be described. It will be shown that IGBT is amenable to fine dialing for soft and hard switching which requires IGBT suppliers to possess sophisticated design, process and applications test capability. The advantages of advanced high voltage IGBTs along with freewheeling diodes will be described for IH quasi-resonant and half-bridge converters. Emphasis will be placed on trench gate IGBT as the most efficient device structure. The power processing efficiency will be presented in terms of overall system efficiency, and particularly, power-loss temperature rise. As a crucial system design criteria for induction heating applications, case or board temperature is emphasized. 1200V, 600V and 1350V platforms, their topology and IGBT device selection will be discussed. The turn off energy (Eoff) and saturation voltage drop (Vcesat) that are optimized by device design represent the most influential factors on system level efficiency and power dissipation. It is shown that precipitous reduction of board temperature of induction cookers is achieved by techniques that simultaneously reduce Eoff and Vcesat.

Technology and design of GaN power devices

This paper reports on the technology and design aspects of an industrial DHEMT process for 650V rated GaN-on-Si power devices, using an in-situ MOCVD grown SiN as surface passivation and gate dielectric, with low interface state density and excellent TDDB. Optimization of the GaN epi stack results in very low off-state leakage (<;10nA/mm). Due to the reduction of buffer trapping, low dynamic Ron (<;10%) is obtained, both at room temperature and at high temperature.

Breakthroughs for 650-V GaN Power Devices: Stable high-temperature operations and avalanche capability

Many prior publications have focused on gallium nitride (GaN) dynamic Rdson issues at room temperature, even though GaN power devices have tremendous advantages over silicon (Si) when serving at high temperatures. We show that room-temperature stable dynamic Rdson behavior does not guarantee device reliability, and it is the stable high-temperature dynamic Rdson that determines the ruggedness of the GaN power devices. With our proprietary and innovative designs and optimizations of epitaxial and device structures, we show a completely different dynamic Rdson behavior in contrast to the common trend reported in the literature: a negative dynamic Rdson trend. We demonstrate robust performance and reliability of our new cascode GaN power devices in PFC tests conducted at both room and high temperatures, at high powers, at high-frequency conditions, and in a totem-pole circuit. We speculate on a physical model to explain the observed dynamic Rdson behaviors in terms of trapping, detrapping, and back-gating effects.

Multi-channel, high-density, ultra-low capacitance arrays for ESD and surge protection

A novel protection device providing ultra-low line capacitance and improved ESD (J. E. Vinson et al., 2003) and surge capability is presented. Applications include stand-alone protection arrays and integrated protection in baseband- or RF-filters. A proprietary epitaxial layer and isolation capability enable high levels of surge power handling capability, while keeping line capacitance low and reducing device footprint. The response of the device to ESD and surge stresses is investigated at wafer- and package-level. Process condition variations and derived structures are studied, along with a consideration of issues related to the measurement of capacitance, ESD and surge capability.

First experimental demonstration of solid state circuit breaker (SSCB) using 650V GaN-based monolithic bidirectional switch

Renewable and other distributed energy resources feed electricity to the utility grid and/or local loads through interfacing power electronic converters. These new microgrids are susceptible to short circuit faults, mandating the use of protective circuit breakers. Solid state circuit breakers (SSCB) are needed due to their much faster response than mechanical circuit breakers. This unique application offers a great market opportunity for normally-on WBG switches. This paper, for the first time, experimentally demonstrates the feasibility of using 650V GaN bidirectional devices in SSCB applications.

3-D TCAD simulation to optimize the trench termination design for higher and robust BVdss

Optimizing the edge termination design around the periphery of active area is critically important for achieving the highest and stable breakdown voltage (BVDSS) for any power devices. Active cell structures can be assumed as two dimensional (2-D) in the central part of the die, however as the active cells terminate to the termination regions at the periphery of the die, 2-D and 3-D transition regions are formed at different locations of the die layout with respect to the last edge termination trench. Optimization of the 3-D termination region is imperative to ascertain equal or higher BVDSS of the termination region than the active cell region. Synopsys advanced multi-dimensional TCAD device simulation tool - “Sentaurus Device Editor (SDE) [1]” is adopted for designing and optimizing the 3-D termination transition region for a higher and robust BVDSS, which is validated by the experimental data.