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Book ChapterDOI

The Dependence of off-State Breakdown of AlGaN/GaN HEMTs on Buffer Traps, Gate Bias and Field Plate

TL;DR: In this paper, the authors investigate AlGaN/GaN HEMTs which show a large increase in measured off-state breakdown voltage, VBR, from near-VT to deep-off state VGS conditions, accompanied by a positive shift in measured VT, when these devices are stressed electrically by alternating ID-VGS and ID−VDS measurements.
Abstract: We investigate AlGaN/GaN HEMTs which show a large increase in measured off-state breakdown voltage, VBR, from near-VT to deep-off state VGS conditions, accompanied by a positive shift in measured VT, when these devices are stressed electrically by alternating ID–VGS and ID–VDS measurements. We show that, if stress is assumed to cause spatially uniform changes, the above variations in VBR and VT can be explained in terms of increased ionized deep acceptor trap concentration in the GaN buffer. We also show that, the near-VT VBR is due to space-charge limited current while the deep off-state VBR is due to impact ionization. Our simulations predict that the incorporation of a field plate in the device can enhance the latter VBR significantly, but may not change the former VBR much.
References
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Journal ArticleDOI
07 Nov 2002
TL;DR: This paper reviews the various trapping phenomena observed in SiC- and GaN-based FETs that contribute to compromised power performance and the measurement techniques utilized to identify these traps.
Abstract: It is well known that trapping effects can limit the output power performance of microwave field-effect transistors (FETs). This is particularly true for the wide bandgap devices. In this paper we review the various trapping phenomena observed in SiC- and GaN-based FETs that contribute to compromised power performance. For both of these material systems, trapping effects associated with both the surface and with the layers underlying the active channel have been identified. The measurement techniques utilized to identify these traps and some of the steps taken to minimize their effects, such as modified buffer layer designs and surface passivation, are described. Since similar defect-related phenomena were addressed during the development of the GaAs technology, relevant GaAs work is briefly summarized.

466 citations

Journal ArticleDOI
TL;DR: In this article, the vertical leakage/breakdown mechanisms in AlGaN/GaN high-electron-mobility transistors grown on low-resistivity p-type (111) Si substrate are studied by temperature-dependent current-voltage (I-V) measurements.
Abstract: Vertical leakage/breakdown mechanisms in AlGaN/GaN high-electron-mobility transistors grown on low-resistivity p-type (111) Si substrate are studied by temperature-dependent current-voltage ( I-V) measurements. It is found that the top-to-substrate vertical breakdown voltage (BV) is dominated by the space-charge-limited current conduction involving both acceptor and donor traps in the GaN buffer/transition layer. From the temperature-dependent transient backgating measurements, the acceptor level at EV + 543 meV and the donor level at EC-616 meV were identified.

173 citations

Journal ArticleDOI
TL;DR: In this article, the physical mechanisms responsible for breakdown current in AlGaN/GaN high electron mobility transistors (HEMTs) were reviewed and compared through a critical comparison between experimental data and previously published results.
Abstract: This paper reviews the physical mechanisms responsible for breakdown current in AlGaN/GaN high electron mobility transistors (HEMTs). Through a critical comparison between experimental data and previously published results we describe the following mechanisms, which can be responsible for the increase in drain current at high drain voltage levels, in the off-state: (i) source–drain breakdown, due to punch-through effects and/or to a poor depletion of the buffer; (ii) vertical (drain-bulk) breakdown, which can be particularly prominent when the devices are grown on a silicon substrate; (iii) breakdown of the gate–drain junction, due either to surface conduction mechanisms or to conduction through the (reverse-biased) Schottky junction at the gate; (iv) impact ionization triggered by hot electrons, that may induce an increase in drain current due to the lowering of the barrier for the injection of electrons from the source.

112 citations

Journal ArticleDOI
TL;DR: In this article, a two-dimensional analysis of breakdown characteristics in field-plate AlGaN/GaN high electron mobility transistors with a relatively short gate length and short gate-to-drain distances is performed by considering a deep donor and a deep acceptor in a buffer layer.
Abstract: The two-dimensional analysis of breakdown characteristics in field-plate AlGaN/GaN high electron mobility transistors with a relatively short gate length and short gate-to-drain distances is performed by considering a deep donor and a deep acceptor in a buffer layer. It is shown that when the acceptor density in the buffer layer is high, the breakdown voltage is determined by the impact ionization of carriers, and it can decrease with increasing the field-plate length. This is because the distance between the field-plate edge and the drain becomes very short and the electric field there becomes very high. On the other hand, when the acceptor density in the buffer layer is relatively low, the buffer leakage current becomes very large and this can determine the breakdown voltage, which becomes very low. In this case, the breakdown voltage increases with increasing the field-plate length.

42 citations