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 article, a critical drain-to-gate voltage beyond which GaN high-electron mobility transistors start to degrade in electrical-stress experiments was found, which is consistent with a degradation mechanism based on crystallographic defect formation due to the inverse piezoelectric effect.
Abstract: We have found that there is a critical drain-to-gate voltage beyond which GaN high-electron mobility transistors start to degrade in electrical-stress experiments. The critical voltage depends on the detailed voltage biasing of the device during electrical stress. It is higher in the OFF state and high-power state than at VDS = 0. In addition, as |VGS| increases, the critical voltage decreases. We have also found that the stress current does not affect the critical voltage although soft degradation at low voltages takes place at high stress currents. All of our findings are consistent with a degradation mechanism based on crystallographic-defect formation due to the inverse piezoelectric effect. Hot-electron-based mechanisms seem to be in contradiction with our experimental results.
300 citations
"Transient stress characterization o..." refers background in this paper
...Electrical degradation is characterized by the onset of gate leakage in the device, loss of power added efficiency, current collapse, change in transconductance, and gate current noise [4, 7, 8]....
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...Electric fields and inverse piezoelectric generated mechanical stress contributions will typically peak here [7] as well as temperature gradients from non-uniform and bias dependent heating [11] which generate stress through thermal expansion....
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TL;DR: In this article, a self-heating in AlGaN/GaN device structures was probed using integrated micro-Raman/Infrared (IR) thermography.
Abstract: Self-heating in AlGaN/GaN device structures was probed using integrated micro-Raman/Infrared (IR) thermography. IR imaging provided large-area-overview temperature maps of powered devices. Micro-Raman spectroscopy was used to obtain high-spatial-resolution temperature profiles over the active area of the devices. Depth scans were performed to obtain temperature in the heat-sinking SiC substrate. Limitations in temperature and spatial resolution, and relative advantages of both techniques are discussed. Results are compared to three-dimensional finite-difference simulations
241 citations
01 Dec 2006
TL;DR: In this paper, the authors carried out systematic experiments of the electrical reliability of state-of-the-art GaN HEMTs and found that degradation is mostly driven by electric field and that there is a critical electric field below which negligible degradation is observed.
Abstract: We have carried out systematic experiments of the electrical reliability of state-of-the-art GaN HEMTs. We have found that degradation is mostly driven by electric field and that there is a critical electric field below which negligible degradation is observed. Device degradation is associated with the appearance of prominent trapping behavior. Degradation is consistent with a model of defect formation in the AlGaN barrier as a result of the high electric field. We postulate that lattice defects are introduced by excessive stress associated with the inverse piezoelectric effect. Electron trapping at these defects reduces the extrinsic sheet carrier concentration and the maximum drain current.
205 citations
TL;DR: In this paper, the temperature distribution in multifinger high-power AlGaN/GaN heterostructure field effect transistors grown on SiC substrates was studied using micro-Raman spectroscopy.
Abstract: The temperature distribution in multifinger high-power AlGaN/GaN heterostructure field-effect transistors grown on SiC substrates was studied. Micro-Raman spectroscopy was used to measure channel temperature with 1 μm spatial resolution, not possible using infrared techniques. Thermal resistance values were determined for four different device layouts with varying number of fingers, finger width, and spacing. The experimental thermal resistance was in fair agreement to that predicted by three-dimensional finite difference heat dissipation simulations. Uncertainties in thermal properties of this device system made simulation less reliable than experiment.
184 citations
TL;DR: In this article, a thermal boundary resistance (TBR) is associated with the presence of an AlN nucleation layer (NL) in AlGaN/GaN high-electron-mobility transistors (HEMTs) grown on SiC substrates.
Abstract: A thermal boundary resistance (TBR) is associated with the presence of an AlN nucleation layer (NL) in AlGaN/GaN high-electron-mobility transistors (HEMTs) grown on SiC substrates, raising device temperature beyond what is expected from the simple thermal conductivities of the main device layers. TBR was found to differ by up to a factor of four between different device suppliers, all using standard metal-organic chemical vapor deposition (MOCVD) growth techniques, related to the detailed NL microstructure. Optimizing the NL crystalline structure in MOCVD could therefore significantly improve heat extraction from AlGaN/GaN HEMTs into the SiC substrate, potentially reducing peak channel temperature rise by up to 40%, significantly benefiting device reliability.
155 citations
"Transient stress characterization o..." refers background in this paper
...A thermal boundary resistance of 60 m(2)KGW is placed at the GaN/SiC interface to account for the AlN nucleation layer [44] (domain not physically modeled for computational speed)....
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