When self-consistency makes a difference

Abstract

T hermal management of semiconductor devices and integrated circuits [from digital to analog and power radio frequency (RF) and microwave circuits] is a wellknown critical issue in modern electronic design. Technology advances, such as device downscaling to increase the maximum operating frequency and the use of wide-bandgap semiconductors [such as silicon carbide and (SiC) and gallium nitride (GaN)] with breakdown voltages one order of magnitude larger than in conventional III-V compounds, have significantly increased power densities in compound semiconductor microwave and mmwave transistors, thus making effective thermal design a key point for successful technology development. Heating is an issue also in Si-based RF technologies, as in lateral double diffused metal oxide semiconductor (LDMOS) devices; however, despite the impressive total RF power such devices exhibit, the power density is in fact much lower, of the order of 1 W/mm against 10 W/mm or more in GaN high electron mobility transistor HEMTs; gallium arsenide GaAs FETs have similar or somewhat larger power densities than LDMOS, but with poorer substrate thermal conductivity. Self-heating not only is a major limitation to the device reliability (through thermal instabilities, hot spot formation, and thermal runaway), but also affects [sometimes in a subtle way, e.g., when long-term thermal memory affects the device linearity (see the "Dynamic Thermal Modeling" section)] the device performance. In many applications, a critical role is also played by the transient thermal response. Examples are pulsed-mode high-power amplifiers (HPAs) (RF and microwave). RF power circuit design

GaN transistor characterization and modeling activities performed within the frame of the KorriGaN project

“…The model can be readily extracted from 3D FEM simulations but also from thermal measurements as well; it allows for a simple and compact circuit implementation within the framework of available circuit simulators, and predicts with high accuracy self-heating dynamics over a wide range of input dissipated power levels and waveforms. Coupled with a temperature-dependent device nonlinear equivalent circuit, it allows for the thermal assessment of GaN-based power amplifiers, including the impact of thermal memory effects on the amplifier linearity [4, 5].…”

Bridging the Gap between Physical and Circuit Analysis for Variability-Aware Microwave Design: Modeling Approaches

“…Therefore, although in principle PIV may be incorporated into the design process, through, e.g., the spread of geometrical dimensions, this is seldom done in actual designs. Thermal simulations are often omitted, unless for applications where temperature is a critical parameter, like in space communication systems [10,11]. EM analyses, however, are almost mandatory at high frequency, as a final tuning/optimization step aimed at taking into account all the coupling effects firstly neglected in circuit-level design.…”

A Wideband Multiharmonic Empirical Large-Signal Model for High-Power GaN HEMTs With Self-Heating and Charge-Trapping Effects

“…Among recently reported analytical, large-signal models for GaN HEMTs [6]- [15], a majority focus on characterizing drain-source current ( ) dispersion from self-heating using dissipated power computations [7]- [10] and charge-trapping effects using transient delay networks [7], [9]. Furthermore, advanced studies on the complex thermal behavior of GaN HEMTs have also been conducted and implemented in large-signal models with good results [11], [12]. However, few report predictions valid beyond 1 A and only a handful report predictions of higher order harmonics [10], [13].…”