Effects of Self-Heating on Performance Degradation in AlGaN/GaN-Based Devices

Benbakhti, B.; Soltani, A.; Kálna, K.; Rousseau, Michel; Jaeger, J.C. de

doi:10.1109/ted.2009.2028400

Cited by 49 publications

(31 citation statements)

References 26 publications

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“…Phonon transport arguments based on the Boltzmann transport equation [see Eq. (12)] suggest that a combination of point defects within the AlN transition layer and near-interface defects around the AlN interfaces may be responsible for the temperature trend of the interface resistance. 44 TDTR measurements on two GaN-AlGaN-diamond composites fabricated using epitaxial transfer reported room temperature interface resistances of 36-47 m 2 K GW −1 and suggested the possibility of achieving ∼30 m 2 K GW −1 at room temperature through the complete etching of the Al-GaN transition layer.…”

Section: Gan-substrate Thermal Interface Resistancementioning

confidence: 99%

Near-Junction Thermal Management: Thermal Conduction in Gallium Nitride Composite Substrates

Cho

Asheghi

et al. 2015

Annual Rev Heat Transfer

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The thermal management challenge posed by gallium nitride (GaN) high-electron-mobility transistor (HEMT) technology has received much attention in the past decade. The peak amplification power density of these devices is limited by heat transfer at the device, substrate, package, and system levels. Thermal resistances within micrometers of the transistor junction can limit efficient heat spreading from active device regions into the substrate and can dominate the overall temperature rise. Gallium nitride composite substrates, which consist of AlGaN/GaN heterostructures with thickness of a few microns on a thicker non-GaN substrate, govern the thermal resistance associated with the "near-junction" region. Silicon and silicon carbide have been widely used as a substrate material, but the performance of GaN devices grown on these substrates is still severely limited by thermal constraints and associated reliability issues. The importance of effective junction-level heat conduction has motivated the development of composite substrates containing high-thermal-conductivity diamond, but these composites require careful attention to thermal resistances between the GaN and the diamond. This chapter reviews thermal conduction phenomena in GaN composite substrates containing Si, SiC, and diamond. The review discusses the governing conduction physics and overviews the relevant measurement techniques. The best available experimental data for GaN composite substrates as well as the relevant thermal modeling are presented. The review concludes with an assessment of the potential benefits of the use of diamond on the device thermal performance.

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Section: Gan-substrate Thermal Interface Resistancementioning

confidence: 99%

Near-Junction Thermal Management: Thermal Conduction in Gallium Nitride Composite Substrates

Cho

Asheghi

et al. 2015

Annual Rev Heat Transfer

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“…15 In the simulation, the self-heating effects in the AlGaN/GaN HEMT is modeled by solving the heat flow equation:…”

Section: Self-heating Effects In Gan Hemtsmentioning

confidence: 99%

Buffer Trap Related Knee Walkout and the Effects of Self-Heating in AlGaN/GaN HEMTs

Ubochi

Ahmeda

Kálna

2017

ECS J. Solid State Sci. Technol.

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Mixed-mode simulations of a class A amplifier is used to study the DC/RF dispersion commonly observed in AlGaN/GaN based HEMTs. We show that the observed knee walkout at frequencies greater than the emission rates of buffer traps (time constants t a e > 1 week) is related to the steady state trap density and spatial location due to the DC operational bias. An increase in the drain bias point and an initial distortion of the RF signal, that is expected to disappear as the device global temperature reduces, is observed when a self-heating model is included. Finally, we propose that a reduction in the DC/RF dispersion is possible with a suitable location and concentration of an acceptor doping in the buffer. Direct current (DC) to radio frequency (RF) dispersion highlighted in experimental studies 1,2 of Gallium Nitride (GaN) based High Electron Mobility Transistors (HEMTs) in the amplifier operation has been attributed to trapping in the device structure. The effect of this dispersion is a reduction in the available RF output power, and effectively results in the reduced performance of GaN HEMTs in RF and power applications in spite of its very promising material properties. The reduction in RF output power can be observed in a so-called knee walkout. The knee walkout describes a situation where the minimum drain voltage under RF drive is smaller than that obtained from DC as opposed to the current collapse (CC) which refers to the reduction in the RF maximum drain current compared to that observed under DC. 3Although experiments have revealed a dependence of the knee walkout on the DC operating point, it remains not understood to what extent degradation processes due to either the surface or the buffer traps affect the device's RF performance. Pulsed measurements of the device have been employed to study the collapse of the current and the dispersion at the knee of the output characteristics, 2 mirroring thus the expected behavior of the device in amplifier operation. This approach is useful in gaining important insights to possible trapping behavior but loses its accuracy in simulations due to the inaccurate determination of the pulsed knee voltage. The simultaneous application of voltages on the drain and the gate contacts in pulsed simulations is in reality achieved with one bias ensuing the other. Here, we have employed a mixed mode simulation of a GaN HEMT in class A operation, which ensures that the instantaneous applied biases depend only on the amplifier operation. The behavior of the device is thus accurately modeled using a physically based device simulator while the remaining part of the circuit is modeled using conventional circuit simulation techniques 4 in a real spirit of TCAD. In addition to the much more realistic simulation approach resulting in increased accuracy, the internal device conditions can be examined at any given point.The investigations are carried out using the drift-diffusion transport model. The study is based on a careful calibration of device I-V characteristics to experimental ...

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“…Two thermodynamic systems, i.e., electrons and acoustic phonons, are assumed to have their own temperatures to be solved for. 14,15 The electron modeling is coupled with the phonon energy conservation equation, in which H in the heat conduction equation is replaced by a collision term between electrons and phonons. This treatment neglects the important contribution from optical phonons.…”

Section: Introductionmentioning

confidence: 99%

A hybrid simulation technique for electrothermal studies of two-dimensional GaN-on-SiC high electron mobility transistors

Hao

Zhao

Xiao

2017

Journal of Applied Physics

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In this work, a hybrid simulation technique is introduced for the electrothermal study of a twodimensional GaN-on-SiC high electron mobility transistor. Detailed electron and phonon transport is considered by coupled electron and phonon Monte Carlo simulations in the transistor region. For regions away from the transistor, the conventional Fourier's law is used for thermal analysis to minimize the computational load. This hybrid simulation strategy can incorporate the physical phenomena over multiple length scales, including phonon generation by hot electrons in the conduction channel, frequency-dependent phonon transport in the transistor region, and heat transfer across the whole macroscale device. Published by AIP Publishing.

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Effects of Self-Heating on Performance Degradation in AlGaN/GaN-Based Devices

Cited by 49 publications

References 26 publications

Near-Junction Thermal Management: Thermal Conduction in Gallium Nitride Composite Substrates

Near-Junction Thermal Management: Thermal Conduction in Gallium Nitride Composite Substrates

Buffer Trap Related Knee Walkout and the Effects of Self-Heating in AlGaN/GaN HEMTs

A hybrid simulation technique for electrothermal studies of two-dimensional GaN-on-SiC high electron mobility transistors

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