Transient stress characterization of AlGaN/GaN HEMTs due to electrical and thermal effects
TL;DR: Finite element simulation results of the transient stress response of an AlGaN/GaN high electron mobility transistor (HEMT) suggest transient failure mechanisms may differ from those previously studied under DC operation due to large amount of cyclic loading of a device around the gate structure.
About: This article is published in Microelectronics Reliability.The article was published on 2015-12-01 and is currently open access. It has received 34 citations till now. The article focuses on the topics: Stress (mechanics) & High-electron-mobility transistor.
Citations
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TL;DR: In this article, gate resistance thermometry (GRT) was used to determine the channel temperature of AlGaN/GaN high electron-mobility transistors under various bias conditions.
Abstract: In this paper, gate resistance thermometry (GRT) was used to determine the channel temperature of AlGaN/GaN high electron-mobility transistors. Raman thermometry has been used to verify GRT by comparing the channel temperatures measured by both techniques under various bias conditions. To further validate this technique, a thermal finite-element model has been developed to model the heat dissipation throughout the devices. Comparisons show that the GRT method averages the temperature over the gate width, yielding a slightly lower peak temperature than Raman thermography. Overall, this method provides a fast and simple technique to determine the average temperature under both steady-state and pulsed bias conditions.
40 citations
Cites background from "Transient stress characterization o..."
...Joule heating mostly occurring in the depletion region and requires the need for electrothermal simulations [16]....
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TL;DR: In this paper, the authors studied the self-heating mechanism and its impact on electrical performance of short gate length GaN high electron mobility transistors (HEMTs) based on electrothermal TCAD simulations.
Abstract: In this paper, we study the self-heating mechanism and its impact on electrical performance of short gate length GaN high electron mobility transistors (HEMTs) based on electrothermal TCAD simulations. We propose an equivalent channel temperature to quantify the current degradation due to self-heating and also resolve the discrepancies between temperature measurements through electrical methods and thermal methods in the literature. We then explain the equivalent channel temperature’s behavior using the temperature- and field-dependent electron transport theory for short gate length HEMTs. The implications and guidelines to the various aspects of device design are also discussed.
39 citations
Cites background from "Transient stress characterization o..."
...Therefore, both the top surface and the two sidewalls are assumed adiabatic [28]....
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TL;DR: In this article, the authors used transient thermoreflectance imaging (TTI) to measure the temperature rise of the passivated gate metal measured by TTI and the averaged gate temperature monitored by gate resistance thermometry (GRT).
Abstract: The development of steady-state thermal characterization techniques for AlGaN/GaN high-electron mobility transistors (HEMTs) has been used to measure the device’s peak temperature under DC conditions. Despite these methods enabling the accurate quantification of the device’s effective thermal resistance and power density dependence, transient thermometry techniques are necessary to understand the nanoscale thermal transport within the active GaN layer where the highly localized joule heating occurs. One technique that has shown the ability to achieve this is transient thermoreflectance imaging (TTI). The accuracy of TTI is based on using the correct thermoreflectance coefficient. In the past, alternative techniques have been used to adjust the thermoreflectance coefficient to match the correct temperature rise in the device. This paper provides a new method to accurately determine the thermoreflectance coefficient of a given surface and is validated via an electrical method: gate resistance thermometry (GRT). Close agreement is shown between the temperature rise of the passivated gate metal measured by TTI and the averaged gate temperature monitored by GRT. Overall, TTI can now be used to thermally map GaN HEMTs under pulsed conditions providing simultaneously a submicrosecond temporal resolution and a submicrometer spatial resolution.
38 citations
Additional excerpts
...transiently powered GaN HEMTs is complex [13]....
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01 Jan 2011
TL;DR: In this article, a physics-based finite element model of operation of an AlGaN/GaN HEMT with device geometry inputs taken from transmission electron microscope cross sections and calibrated by comparison with measured electrical data comprising standard field-effect transistor metrics and less well-known model parameters is presented.
Abstract: : We present a physics-based finite-element model of operation of an AlGaN/GaN HEMT with device geometry inputs taken from transmission electron microscope cross sections and calibrated by comparison with measured electrical data comprising standard field-effect transistor metrics and less well-known model parameters. A variety of electrical outputs from the model are compared to experiment, and the level of agreement is reported.
17 citations
21 Mar 2021
TL;DR: In this paper, the surge-energy robustness of a 650-V rated cascode GaN HEMT in the unclamped inductive clamping (UIS) test was investigated.
Abstract: Surge energy robustness of power devices is highly desired in many power applications such as automotive powertrains and power grids. While Si and SiC power MOSFETs withstand surge energy through avalanching, GaN high-electron-mobility transistors (HEMTs) have no avalanche capability. Recent studies have revealed that the p-gate GaN HEMT withstands surge energy through capacitive charging and fails when the peak capacitive voltage reaches its breakdown voltage (BV). This work, for the first time, studies the surge-energy robustness of a 650-V rated cascode GaN HEMT in the unclamped inductive clamping (UIS) test. The cascode GaN HEMT was found to withstand the surge energy via capacitive charging but accompanied by the Si MOSFET avalanching. Two failure modes were observed, both occurring in the GaN HEMT. The first mode is featured by a short between the HEMT gate and drain (cascode source and drain), while the second mode is featured by a short between the HEMT source and drain. Statistical results of multiple devices tested under different load inductance show that the second failure mode predominates. Additionally, the device failure voltage in mode I is statistically higher than that in mode II. Failure analysis of both modes is presented, and the physical explanations of the two modes and their competitions are proposed. These results provide important new insights into the robustness of cascode GaN HEMTs.
16 citations
References
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TL;DR: In this paper, the thermal response of AlGaN/GaN high electron mobility transistors was examined via micro-Raman spectroscopy under various bias conditions where power dissipation levels were identical.
Abstract: The thermal response of AlGaN/GaN high electron mobility transistors directly correlates with the overall performance and reliability of these devices. In general, a hot spot develops near the drain end of the gate electrode during power dissipation. The device channel temperature was examined via micro-Raman spectroscopy under various bias conditions where power dissipation levels were identical. Under these bias conditions, difference in internal states (sheet carrier density and electric held distribution) within the device alters the heat generation profile across the channel. High Vds conditions lead to significantly higher channel temperature compared to that for low Vds conditions although the power dissipation is kept constant. Experimental results show ~13°C deviation between Vds = 45 V and Vds = 7 V cases when the power dissipation is 4.5 W/mm. This suggests that bias conditions may have a relatively signihcant impact on device reliability and that this effect must be considered when building thermal models of devices under operation or undergoing accelerated life testing.
65 citations
Additional excerpts
...spreading of the heat generation region [27, 28]....
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TL;DR: It is shown that operating bias condition has a significant role in device reliability by altering value and location of the peak temperature, which then alters the type and rate of thermally induced degradation taking place at critical locations such as the drain side corner of the gate.
58 citations
"Transient stress characterization o..." refers result in this paper
...These results are consistent with similar numerical models from literature [27]....
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...spreading of the heat generation region [27, 28]....
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TL;DR: In this paper, coupled electro-thermo-mechanical simulation and Raman thermometry were used to analyze the evolution of mechanical stress in AlGaN/GaN high electron mobility transistors (HEMTs).
Abstract: Coupled electro-thermo-mechanical simulation and Raman thermometry were utilized to analyze the evolution of mechanical stress in AlGaN/GaN high electron mobility transistors (HEMTs). This combined analysis was correlated with electrical step stress tests to determine the influence of mechanical stress on the degradation of actual devices under diverse bias conditions. It was found that the total stress as opposed to one dominant stress component correlated the best with the degradation of the HEMT devices. These results suggest that minimizing the total stress as opposed to the inverse piezoelectric stress in the device is necessary in order to avoid device degradation which can be accomplished through various growth methods.
55 citations
"Transient stress characterization o..." refers background or methods in this paper
...Several researchers have outlined these effects within devices, but the underlying mechanisms for degradation has yet to be fully understood [4-6]....
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...For this work, material properties were chosen from literature based upon values that have been previously verified through numerical simulations and experimental results [6, 29]....
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...In addition, residual stresses exist due to fabrication processes [6, 12-15]....
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...A thermal boundary resistance is applied at the GaN/SiC interface to account for the thermal resistance of the AlN nucleation layer [6, 29]....
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...This manuscript version is made available under the Elsevier user license http://www.elsevier.com/open-access/userlicense/1.0/ on the order of 1-3 GPa [6, 12] from pseudomorphic growth on GaN....
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TL;DR: In this paper, the thermal properties of AlGaN/GaN heterostructure field effect transistors grown on semi-insulating bulk GaN substrates were studied using micro-Raman thermography, microphotoluminescence spectroscopy, and thermal simulation.
Abstract: Micro-Raman thermography, microphotoluminescence spectroscopy, and thermal simulation were used to study the thermal properties of AlGaN/GaN heterostructure field-effect transistors grown on semi-insulating bulk GaN substrates. A bulk GaN thermal conductivity of 260 was determined from temperature measurements on operating devices in combination with finite-difference thermal simulations. This is significantly higher than typical thin GaN epilayer thermal conductivities, due to a lower dislocation density in bulk GaN. Despite the thermal conductivity of bulk GaN being lower than that of SiC, transistors on bulk GaN exhibited a similar thermal resistance as GaN-on-SiC devices, attributed to the absence of a thermal boundary resistance between the device epilayers and substrate for GaN-on-GaN devices.
53 citations
17 Apr 2007
TL;DR: In this article, the authors present the latest results for GaN device reliability benchmarking and show that GaN devices have the capability of satisfying system device requirements from UHF through millimeter-wave.
Abstract: Wide bandgap (WBG) devices offer significant advantages for next generation military and commercial systems. SiC MESFETs currently achieve power densities of 4.0 W/mm with power added efficiencies in excess of 60% on a repeatable basis. They are commercially available in packaged or die formats and have been successfully designed into a number of systems. GaN is also extremely promising as a next generation wide bandgap device. Cree has demonstrated power densities higher than 25 watts per mm of gate periphery. With ftau's > 40 GHz, GaN devices have the capability of satisfying system device requirements from UHF through millimeter-wave. Both technologies are now also offered through commercial MMIC foundry services using design rules and non-linear models provided for external designers. Significant progress has also been made in the development of 100-mm SiC substrates and WBG epitaxy (SiC and GaN) which is key for commercializing the technology and providing low costs. Micropipe densities as low as 2.5 cm-2 have been demonstrated for 100-mm HPSI substrates and both SiC and GaN epitaxy with excellent intra-wafer sheet resistance uniformity have been demonstrated. With robust reliability for SiC MESFETs now established for several years, the latest results for GaN device reliability benchmarking are shown.
42 citations
"Transient stress characterization o..." refers background in this paper
...4 eV at room temperature) semiconductor with a promising combination of material properties including a high electric breakdown field, good electron mobility, high saturation velocity, relatively high thermal conductivity, and is stable at high operating temperatures [1]; all of which contribute to making these devices very suitable for RF devices where high power and high frequency operation are needed [2, 3]....
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