Surge-Energy and Overvoltage Ruggedness of P-Gate GaN HEMTs
TL;DR: In this article, a commercial p-gate GaN high-electron-mobility transistor (HEMT) with Ohmic-and Schottky-type gate contacts is studied.
Abstract: An essential ruggedness of power devices is the capability of safely withstanding the surge energy. The surge ruggedness of the GaN high-electron-mobility transistor (HEMT), a power transistor with no or minimal avalanche capability, has not been fully understood. This article unveils the comprehensive physics associated with the surge-energy withstand process and the failure mechanisms of p-gate GaN HEMTs. Two commercial p-gate GaN HEMTs with Ohmic- and Schottky-type gate contacts are studied. Two circuits are developed to study the device surge ruggedness: an unclamped inductive switching circuit is first used to identify the withstand dynamics and failure mechanisms, and a clamped inductive switching circuit with a controllable parasitic inductance is then designed to mimic the surge energy in converter-like switching events. The p-gate GaN HEMT is found to withstand the surge energy through a resonant energy transfer between the device capacitance and the load/parasitic inductance rather than a resistive energy dissipation as occurred in the avalanche. If the device resonant voltage goes below zero, the device reversely turns on and the inductor is discharged. The device failure occurs at the transient of peak resonant voltage and is limited by the device overvoltage capability rather than the surge energy, dV/dt , or overvoltage duration. Almost no energy is dissipated in the resonant withstand process and the device failure is dominated by an electric field rather than a thermal runaway. These results provide critical understandings on the ruggedness of GaN HEMTs and important references for their qualifications and applications.
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TL;DR: In this article, the authors provide a glimpse of future GaN device technologies and advanced modeling approaches that can push the boundaries of these applications in terms of performance and reliability, which is a key missing piece to realize the full GaN platform with integrated digital, power, and RF electronics technologies.
Abstract: GaN technology is not only gaining traction in power and RF electronics but is also rapidly expanding into other application areas including digital and quantum computing electronics. This paper provides a glimpse of future GaN device technologies and advanced modeling approaches that can push the boundaries of these applications in terms of performance and reliability. While GaN power devices have recently been commercialized in the 15–900 V classes, new GaN devices are greatly desirable to explore both higher-voltage and ultra-low-voltage power applications. Moving into the RF domain, ultra-high frequency GaN devices are being used to implement digitized power amplifier circuits, and further advances using the hardware–software co-design approach can be expected. On the horizon is the GaN CMOS technology, a key missing piece to realize the full-GaN platform with integrated digital, power, and RF electronics technologies. Although currently a challenge, high-performance p-type GaN technology will be crucial to realize high-performance GaN CMOS circuits. Due to its excellent transport characteristics and ability to generate free carriers via polarization doping, GaN is expected to be an important technology for ultra-low temperature and quantum computing electronics. Finally, given the increasing cost of hardware prototyping of new devices and circuits, the use of high-fidelity device models and data-driven modeling approaches for technology-circuit co-design are projected to be the trends of the future. In this regard, physically inspired, mathematically robust, less computationally taxing, and predictive modeling approaches are indispensable. With all these and future efforts, we envision GaN to become the next Si for electronics.
83 citations
TL;DR: In this paper, the authors describe the high-temperature performance and avalanche capability of normally-off 1.2-K V-class vertical gallium nitride (GaN) fin-channel junction field effect transistors (Fin-JFETs).
Abstract: This work describes the high-temperature performance and avalanche capability of normally- off 1.2-K V-CLASS vertical gallium nitride (GaN) fin-channel junction field-effect transistors (Fin-JFETs). The GaN Fin-JFETs were fabricated by NexGen Power Systems, Inc. on 100-mm GaN-on-GaN wafers. The threshold voltage ( ${V}_{\text {TH}}$ ) is over 2 V with less than 0.15 V shift from 25 °C to 200 °C. The specific ON-resistance ( ${R}_{ \mathrm{\scriptscriptstyle ON}}$ ) increases from 0.82 at 25 °C to 1.8 $\text{m}\Omega \cdot $ cm2 at 200 °C. The thermal stability of ${V}_{\text {TH}}$ and ${R}_{ \mathrm{\scriptscriptstyle ON}}$ are superior to the values reported in SiC MOSFETs and JFETs. At 200 °C, the gate leakage and drain leakage currents remain below $100~\mu \text{A}$ at −7-V gate bias and 1200-V drain bias, respectively. The gate leakage current mechanism is consistent with carrier hopping across the lateral p-n junction. The high-bias drain leakage current can be well described by the Poole–Frenkel (PF) emission model. An avalanche breakdown voltage ( $BV_{\!\!\text {AVA}}$ ) with positive temperature coefficient is shown in both the quasi-static ${I}$ – ${V}$ sweep and the unclamped inductive switching (UIS) tests. The UIS tests also reveal a $BV_{\!\!\text {AVA}}$ over 1700 V and a critical avalanche energy ( ${E}_{\text {AVA}}$ ) of 7.44 J/cm2, with the ${E}_{\text {AVA}}$ comparable to that of state-of-the-art SiC MOSFETs. These results show the great potentials of vertical GaN Fin-JFETs for medium-voltage power electronics applications.
63 citations
TL;DR: In this article, the authors present a global overview of the reported GaN FinFET and trigate device technologies for RF and power applications, as well as provide in-depth analyses correlating device design parameters to device performance space.
Abstract: Gallium nitride (GaN) is becoming a mainstream semiconductor for power and radio-frequency (RF) applications. While commercial GaN devices are increasingly being adopted in data centers, electric vehicles, consumer electronics, telecom and defense applications, their performance is still far from the intrinsic GaN limit. In the last few years, the fin field-effect transistor (FinFET) and trigate architectures have been leveraged to develop a new generation of GaN power and RF devices, which have continuously advanced the state-of-the-art in the area of microwave and power electronics. Very different from Si digital FinFET devices, GaN FinFETs have allowed for numerous structural innovations based on engineering the two-dimensional-electron gas or p–n junctions, in both lateral and vertical architectures. The superior gate controllability in these fin-based GaN devices has not only allowed higher current on/off ratio, steeper threshold swing, and suppression of short-channel effects, but also enhancement-mode operation, on-resistance reduction, current collapse alleviation, linearity improvement, higher operating frequency, and enhanced thermal management. Several GaN FinFET and trigate device technologies are close to commercialization. This review paper presents a global overview of the reported GaN FinFET and trigate device technologies for RF and power applications, as well as provides in-depth analyses correlating device design parameters to device performance space. The paper concludes with a summary of current challenges and exciting research opportunities in this very dynamic research field.
54 citations
TL;DR: In this paper, the dynamic breakdown voltage (BV) and overvoltage margin of a 650-V-rated commercial GaN power HEMT in hard switching were studied. And the results suggest that the BV and over voltage margin of HEMTs in practical power switching can be significantly underestimated using the static BV.
Abstract: This work studies the dynamic breakdown voltage (BV) and overvoltage margin of a 650-V-rated commercial GaN power HEMT in hard switching. The dynamic BV measured in the hard switching circuits is over 1.4 kV, being 450 V higher than the static BV measured in the quasi-static I-V sweep. The device can survive at least 1 million hard-switching overvoltage pulses with 1.33 kV peak overvoltage (~95% dynamic BV). Recoverable device parametric shifts are observed after the 1-million pulses, featuring small reductions in threshold voltage and on-resistance. These shifts are different from the ones after the hard-switching pulses without overvoltage and are attributable to the trapping of the holes produced in impact ionization. These results suggest that the BV and overvoltage margin of GaN HEMTs in practical power switching can be significantly underestimated using the static BV.
53 citations
TL;DR: In this article, the authors present the first experimental demonstrations of large-area Ga2O3 Schottky barrier diodes (SBDs) packaged in the bottom-side-cooling and double-sidecooling configurations, and for the first time, characterizes the surge current capabilities of these packaged SBDs.
Abstract: Ultrawide-bandgap gallium oxide (Ga2O3) devices have recently emerged as promising candidates for power electronics; however, the low thermal conductivity ( k T) of Ga2O3 causes serious concerns about their electrothermal ruggedness. This letter presents the first experimental demonstrations of large-area Ga2O3 Schottky barrier diodes (SBDs) packaged in the bottom-side-cooling and double-side-cooling configurations, and for the first time, characterizes the surge current capabilities of these packaged Ga2O3 SBDs. Contrary to popular belief, Ga2O3 SBDs with proper packaging show high surge current capabilities. The double-side-cooled Ga2O3 SBDs with a 3 × 3-mm2 Schottky contact area can sustain a peak surge current over 60 A, with a ratio between the peak surge current and the rated current superior to that of similarly-rated commercial SiC SBDs. The key enabling mechanisms for this high surge current are the small temperature dependence of on -resistance, which strongly reduces the thermal runaway, and the double-side-cooled packaging, in which the heat is extracted directly from the Schottky junction and does not need to go through the low- k T bulk Ga2O3 chip. These results remove some crucial concerns regarding the electrothermal ruggedness of Ga2O3 power devices and manifest the significance of their die-level thermal management.
52 citations
References
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TL;DR: In this article, the characteristics and commercial status of both vertical and lateral GaN power devices are reviewed, providing the background necessary to understand the significance of these recent developments and the challenges encountered in GaN-based converter design, such as the consequences of faster switching on gate driver and board layout.
Abstract: Gallium nitride (GaN) power devices are an emerging technology that have only recently become available commercially. This new technology enables the design of converters at higher frequencies and efficiencies than those achievable with conventional Si devices. This paper reviews the characteristics and commercial status of both vertical and lateral GaN power devices, providing the background necessary to understand the significance of these recent developments. In addition, the challenges encountered in GaN-based converter design are considered, such as the consequences of faster switching on gate driver design and board layout. Other issues include the unique reverse conduction behavior, dynamic $R_{\mathrm {{ds}},\mathrm {{on}}}$ , breakdown mechanisms, thermal design, device availability, and reliability qualification. This review will help prepare the reader to effectively design GaN-based converters, as these devices become increasingly available on a commercial scale.
769 citations
Additional excerpts
...mercial p-gate GaN HEMTs with Ohmic- and Schottky-type gate contacts, the two mainstream enhancement-mode (E-mode) GaN power transistors [13]....
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164 citations
"Surge-Energy and Overvoltage Rugged..." refers methods in this paper
...The acceptor-like traps were added into the GaN buffer layer in the simulation based on the experimental reports on GaN-on-Si devices [20],...
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TL;DR: In this article, the authors demonstrated GaN vertical Schottky and p-n diodes on Si substrates for the first time, achieving a breakdown voltage of 205 V and a soft BV higher than 300 V, respectively, with peak electric field of 2.9 MV/cm in GaN.
Abstract: This letter demonstrates GaN vertical Schottky and p-n diodes on Si substrates for the first time. With a total GaN drift layer of only 1.5- $\mu{\rm m}$ thick, a breakdown voltage (BV) of 205 V was achieved for GaN-on-Si Schottky diodes, and a soft BV higher than 300 V was achieved for GaN-on-Si p-n diodes with a peak electric field of 2.9 MV/cm in GaN. A trap-assisted space-charge-limited conduction mechanism determined the reverse leakage and breakdown mechanism for GaN-on-Si vertical p-n diodes. The on-resistance was 6 and 10 ${\rm m}\Omega\cdot{\rm cm}^{2}$ for the vertical Schottky and p-n diode, respectively. These results show the promising performance of GaN-on-Si vertical devices for future power applications.
158 citations
Additional excerpts
...[21]....
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TL;DR: In this article, the authors present self-consistent electrothermal simulations of single-finger and multifinger GaN vertical metal-oxide-semiconductor field effect transistors (MOSFETs) and lateral AlGaN/GaN high-electron-mobility transistors and compare their thermal performance.
Abstract: In this paper, we present self-consistent electrothermal simulations of single-finger and multifinger GaN vertical metal-oxide-semiconductor field-effect transistors (MOSFETs) and lateral AlGaN/GaN high-electron-mobility transistors (HEMTs) and compare their thermal performance. The models are first validated by comparison with experimental dc characteristics, and then used to study the maximum achievable power density of the device without the peak temperature exceeding a safe operation limit of 150°C (P150°C). It is found that the vertical MOSFETs have the potential to achieve a higher P150°C than the lateral HEMTs, especially for higher breakdown voltages and higher scaling level designs.
140 citations
"Surge-Energy and Overvoltage Rugged..." refers methods in this paper
...The physical models for device simulation were based on the ones described in [18] and [19], and the static simulation...
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TL;DR: In this paper, the small-angle beveled field plate (SABFP) was used to fabricate a very small bevel angle (∼ 1°) in the mesa and field plates.
Abstract: This letter demonstrates vertical Ga2O3 Schottky barrier diodes (SBDs) with a novel edge termination, the small-angle beveled field plate (SABFP), fabricated on thinned $\text{G}_{{2}}\text{O}_{{3}}$ substrates. Non-punch-though design is used for the drift region with a donor concentration of ${3}\sim {3.5} \times {10} ^{{16}}$ cm−3, rendering a device differential ON-resistance of $\sim 2~\text{m}\Omega ~\cdot $ cm2. A new wet-etch technique is developed by using a bi-layer mask, which consists of spin-on-glass (SOG) and plasma-enhanced chemical vapor deposited (PECVD) SiO2, to fabricate a very small bevel angle (∼ 1°) in the mesa and field plates. This SABFP structure facilitates the electric field spreading at device edges, rendering a breakdown voltage of 1100 V, a peak electric field of 3.5 MV/cm in Ga2O3 at the Schottky contact edge, and an averaged electric field over 3.4 MV/cm underneath the contact. Our device demonstrates a Baliga’s figure of merit of 0.6 GW/cm2, which is among the highest in all reported Ga2O3 power devices and comparable to the state-of-the-art GaN SBDs. These results show the great potential of Ga2O3 SBDs for future power applications.
131 citations
"Surge-Energy and Overvoltage Rugged..." refers methods in this paper
...5 MV/cm, which is below the critical E-field of SiNx or SiO2 (∼10 MV/cm [24]), the commonly used dielectric materials for passivation...
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