Understanding the effects of off-state and hard-switching stress in gallium nitride-based power transistors

Journal of Applied Physics

Abid

et al. 2021

Self Cite

346

126

Over the last decade, gallium nitride has emerged as an excellent material for the fabrication of power devices. Among the semiconductors for which power devices are already available on the market, GaN has the widest energy gap, the largest critical field, the highest saturation velocity, thus representing an excellent material for the fabrication of high speed/high voltage components.The presence of spontaneous and piezoelectric polarization allows to create a 2-dimensional electron gas, with high mobility and large channel density, in absence of any doping, thanks to the use of AlGaN/GaN heterostructures. This contributes to minimize resistive losses; at the same time, for GaN transistors switching losses are very low, thanks to the small parasitic capacitances and switching charges. Device scaling and monolithic integration enable high frequency operation, with consequent advantages in terms of miniaturization.For high power/high voltage operation, vertical device architectures are being proposed and investigated, and 3-dimensional structuresfin-shaped, trench-structured, nanowire-basedare demonstrating a great potential. Contrary to silicon, GaN is a relatively young material: trapping and degradation processes must be understood and described in detail, with the aim of optimizing device stability and reliability. This tutorial paper describes the physics, technology and reliability of GaN-based power devices: in the first part of the article, starting from a discussion of the main properties of the material, the characteristics of lateral and vertical GaN transistors are discussed in detail, to provide guidance in this complex and interesting field. The second part of the paper focuses on trapping and reliability aspects: the physical origin of traps in GaN, and the main degradation mechanisms are discussed in detail. The wide set of referenced papers and the insight on the most relevant aspects gives the reader a comprehensive overview on present and next-generation GaN electronics. IntroductionOver the past decade, gallium nitride has emerged as an excellent material for the fabrication of power semiconductor devices. Thanks to the unique properties of GaN, diodes and transistors based on this material have excellent performance, compared to their silicon counterparts, and are expected to find wide application in the next-generation power converters. Owing to the flexibility and the energy efficiency of GaN-based power converters, the interest towards this technology is rapidly growing: the aim of this tutorial is to review the most relevant physical properties, the operating principles, the fabrication parameters, and the stability/reliability issues of GaN-based power transistors. For introductory purposes, we start summarizing the physical reasons why GaN transistors achieve a much better performance than the corresponding silicon devices, to help the reader understanding the unique advantages of this technology.The properties of GaN devices allow the fabrication of high-efficiency (near or above 99 %)...

Section: Current Transientsmentioning

confidence: 99%

Section: Bias Conditionsmentioning

confidence: 99%

Section: Semi-on-statementioning

confidence: 99%

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GaN-based power devices: Physics, reliability, and perspectives

Meneghini

Journal of Applied Physics

Abid

et al. 2021

Self Cite

346

126

“…Based on these considerations, we demonstrate the applicability of the developed mathematical framework to the trap-state mapping in in normally-off p-GaN HEMTs after semi-on stress. During this stress condition, the device must sustain a simultaneously high drain-to-gate electric field and carrier density 26 . The carriers accelerated by the high field are described as “hot”, and their excess kinetic energy may favor trapping effects that are not reachable under normal (off-state) conditions.…”

Section: Experimental Trap-state Mapping On Gan-based Transistorsmentioning

confidence: 99%

Trap-state mapping to model GaN transistors dynamic performance

Modolo

Minetto

et al. 2022

Sci Rep

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Trapping phenomena degrade the dynamic performance of wide-bandgap transistors. However, the identification of the related traps is challenging, especially in presence of non-ideal defects. In this paper, we propose a novel methodology (trap-state mapping) to extract trap parameters, based on the mathematical study of stretched exponential recovery kinetics. To demonstrate the effectiveness of the approach, we use it to identify the properties of traps in AlGaN/GaN transistors, submitted to hot-electron stress. After describing the mathematical framework, we demonstrate that the proposed methodology can univocally describe the properties of the distribution of trap states. In addition, to prove the validity and the usefulness of the model, the trap properties extracted mathematically are used as input for TCAD simulations. The results obtained by TCAD closely match the experimental transient curves, thus confirming the accuracy of the trap-state mapping procedure. This methodology can be adopted also on other technologies, thus constituting a universal approach for the analysis of multiexponential trapping kinetics.

“…Such trapping phenomena need to be analyzed and modeled: state-of-the-art approaches [15]- [17] reproduce trapping/detrapping phenomena as pure exponentials, an approximation that is only valid for ideal point defects, with a single energy level; following this idea, Kellogg et al [16] proposed a method to model defects in GaN HEMTs making use of a three-pole RC circuit. However, pure exponentials are generally not representative of real trapping kinetics [18]. In the presence of multiple traps, Li et al [17] suggested an iterative algorithm to extract multiple RC units with minimized error.…”

mentioning

confidence: 99%

Compact Modeling of Nonideal Trapping/Detrapping Processes in GaN Power Devices

Modolo

IEEE Trans. Electron Devices

Baratella

et al. 2022

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Compact modeling of charge trapping processes in GaN transistors is of fundamental importance for advanced circuit design. The goal of this article is to propose a methodology for modeling the dynamic characteristics of GaN power HEMTs in the realistic case where trapping/detrapping kinetics are described by stretched exponentials, contrary to ideal pure exponentials, thus significantly improving the state of the art. The analysis is based on: 1) an accurate methodology for describing stretched-exponential transients and extracting the related parameters and 2) a novel compact modeling approach, where the stretched exponential behavior is reproduced via multiple RC networks, whose parameters are specifically tuned based on the results of 1). The developed compact model is then used to simulate the transient performance of the HEMT devices as a function of duty cycle and frequency, thus providing insight on the impact of traps during the realistic switching operation.