Leakage mechanism in GaN and AlGaN Schottky interfaces
TL;DR: In this paper, the mechanism of leakage currents through GaN and AlGaN Schottky interfaces is discussed based on detailed temperature-dependent current-voltage (I-V-T) measurements.
Abstract: Based on detailed temperature-dependent current–voltage (I–V–T) measurements the mechanism of leakage currents through GaN and AlGaN Schottky interfaces is discussed. The experiments were compared to calculations based on thin surface barrier model in which the effects of surface defects were taken into account. Our simulation method reproduced the experimental I–V–T characteristics of the GaN and AlGaN Schottky diodes, and gave excellent fitting results to the reported Schottky I–V curves in GaN for both forward and reverse biases at different temperatures. The present results indicate that the barrier thinning caused by unintentional surface-defect donors enhances the tunneling transport processes, leading to large leakage currents through GaN and AlGaN Schottky interfaces.
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TL;DR: In this paper, a method with an accurate control of threshold voltages of AlGaN/GaN high-electron mobility transistors (HEMTs) using a fluoride-based plasma treatment was presented.
Abstract: This paper presents a method with an accurate control of threshold voltages (Vth) of AlGaN/GaN high-electron mobility transistors (HEMTs) using a fluoride-based plasma treatment. Using this method, the Vth of AlGaN/GaN HEMTs can be continuously shifted from -4 V in a conventional depletion-mode (D-mode) AlGaN/GaN HEMT to 0.9 V in an enhancement-mode AlGaN/GaN HEMT. It was found that the plasma-induced damages result in a mobility degradation of two-dimensional electron gas. The damages can be repaired and the mobility can be recovered by a post-gate annealing step at 400 degC. At the same time, the shift in Vth shows a good thermal stability and is not affected by the post-gate annealing. The enhancement-mode HEMTs show a performance (transconductance, cutoff frequencies) comparable to the D-mode HEMTs. Experimental results confirm that the threshold-voltage shift originates from the incorporation of F ions in the AlGaN barrier. In addition, the fluoride-based plasma treatment was also found to be effective in lowering the gate-leakage current, in both forward and reverse bias regions. A physical model of the threshold voltage is proposed to explain the effects of the fluoride-based plasma treatment on AlGaN/GaN HEMTs
489 citations
Cites background from "Leakage mechanism in GaN and AlGaN ..."
...dominated by the TE mechanism but other mechanisms, such as vertical tunneling [38], surface barrier thinning [39], and...
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TL;DR: In this paper, the advantages and limitations of the current-transient methods used for the study of the deep levels in GaN-based high-electron mobility transistors (HEMTs), by evaluating how the procedures adopted for measurement and data analysis can influence the results of the investigation.
Abstract: This paper critically investigates the advantages and limitations of the current-transient methods used for the study of the deep levels in GaN-based high-electron mobility transistors (HEMTs), by evaluating how the procedures adopted for measurement and data analysis can influence the results of the investigation. The article is divided in two parts within Part I. 1) We analyze how the choice of the measurement and analysis parameters (such as the voltage levels used to induce the trapping phenomena and monitor the current transients, the duration of the filling pulses, and the method used for the extrapolation of the time constants of the capture/emission processes) can influence the results of the drain current transient investigation and can provide information on the location of the trap levels responsible for current collapse. 2) We present a database of defects described in more than 60 papers on GaN technology, which can be used to extract information on the nature and origin of the trap levels responsible for current collapse in AlGaN/GaN HEMTs. Within Part II, we investigate how self-heating can modify the results of drain current transient measurements on the basis of combined experimental activity and device simulation.
320 citations
Additional excerpts
...[26], [55], [67]; or 3) deep-levels charge de-trapping by electron trap-assisted-tunneling mechanisms [14], [15], [54], [60], [70]....
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TL;DR: A comprehensive review of solar-blind photodetectors based on gallium oxide (Ga2O3) materials in various forms of bulk single crystal, epitaxial films, nanostructures, and their ternary alloys is presented in this paper.
Abstract: Solar-blind photodetectors are of great interest to a wide range of industrial, civil, environmental, and biological applications. As one of the emerging ultrawide-bandgap semiconductors, gallium oxide (Ga2O3) exhibits unique advantages over other wide-bandgap semiconductors, especially in developing high-performance solar-blind photodetectors. This paper comprehensively reviews the latest progresses of solar-blind photodetectors based on Ga2O3 materials in various forms of bulk single crystal, epitaxial films, nanostructures, and their ternary alloys. The basic working principles of photodetectors and the fundamental properties and synthesis of Ga2O3, as well as device processing developments, have been briefly summarized. A special focus is to address the physical mechanism for commonly observed huge photoconductive gains. Benefitting from the rapid development in material epitaxy and device processes, Ga2O3-based solar-blind detectors represent to date one of the most prospective solutions for UV detection technology towards versatile applications.
306 citations
TL;DR: In this paper, a planar Schottky photovoltaic device was constructed from solution-processed PbS nanocrystal quantum dot films with aluminum and indium tin oxide contacts.
Abstract: Planar Schottky photovoltaic devices were prepared from solution-processed PbS nanocrystal quantum dot films with aluminum and indium tin oxide contacts. These devices exhibited up to 4.2% infrared power conversion efficiency, which is a threefold improvement over previous results. Solar power conversion efficiency reached 1.8%. The simple, optimized architecture allows for direct implementation in multijunction photovoltaic device configurations.
267 citations
Cites background from "Leakage mechanism in GaN and AlGaN ..."
...In practice though, barrier height dependence on electric field and tunnelling effects lead to a bias-dependent current in reverse bias [109, 115]....
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References
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TL;DR: In this article, the authors derived voltage-current characteristics for field and T-F emission in the forward and reverse regime of Schottky barriers formed on highly doped semiconductors.
Abstract: Field emission and thermionic-field (T-F) emission are considered as the phenomena responsible for the excess currents observed both in the forward and reverse directions of Schottky barriers formed on highly doped semiconductors. Voltage-current characteristics are derived for field and thermionic-field emission in the forward and reverse regime. The temperatures and voltages where these phenomena are predominent for a given diode are discussed. Comparison with experimental results on GaAs and Si diodes shows good agreement between theory and experiments.
1,268 citations
PARC1
TL;DR: In this article, the electronic structure, atomic geometry, and formation energies of native defects in GaN using first-principles total energy calculations were studied, and it was shown that the vacancies are the dominant defects in the GaN, whereas antisites and interstitials are less favorable.
Abstract: We have studied the electronic structure, atomic geometry, and formation energies of native defects in GaN using first-principles total-energy calculations. Our results reveal the vacancies to be the dominant defects in GaN, whereas antisites and interstitials are energetically less favorable. In p-type GaN the nitrogen vacancy (a donor) has the lowest formation energy, in n-type GaN the gallium vacancy (an acceptor). Our results show that the vacancies may be important for compensation. However, isolated point defects and particularly the nitrogen vacancy can be excluded as the source for the n-type conductivity in as-grown GaN, contrary to the generally accepted picture.
683 citations
TL;DR: In this article, temperature-dependent current-voltage measurements have been used to determine the reverse-bias leakage current mechanisms in Schottky diodes fabricated on GaN grown by molecular-beam epitaxy.
Abstract: Temperature-dependent current–voltage measurements have been used to determine the reverse-bias leakage current mechanisms in Schottky diodes fabricated on GaN grown by molecular-beam epitaxy, and two dominant mechanisms are clearly identified. The first mechanism is field-emission tunneling from the metal into the semiconductor, which is dominant at low temperatures and which, at higher temperatures, becomes significant for large reverse-bias voltages. The second mechanism, presumed to be associated with dislocation-related leakage current paths, is observed to have an exponential temperature dependence and becomes significant above approximately 275 K. The temperature dependence of the second mechanism is consistent with either one-dimensional variable-range-hopping conduction along the dislocation or trap-assisted tunneling.
260 citations
TL;DR: In this paper, the authors investigated the mechanisms of drain current collapse and gate leakage currents in the AlGaN/GaN heterostructure field effect transistor (HFET), and detailed electrical properties of the ungated and Schottky-gated portion of the device were investigated separately.
Abstract: In order to clarify the mechanisms of drain current collapse and gate leakage currents in the AlGaN/GaN heterostructure field effect transistor (HFET), detailed electrical properties of the ungated portion and Schottky-gated portion of the device were investigated separately, using a gateless HFET structure and an AlGaN Schottky diode structure. The gateless device was subjected to plasma treatments and surface passivation processes including our novel Al2O3-based surface passivation. dc I–V curves of gateless HFETs were highly nonlinear due to virtual gating by surface states. After drain stress, air-exposed, H2 plasma-treated and SiO2-deposited gateless HFETs showed an initial large-amplitude exponential current transient followed by a subsequent smaller, slow, and highly nonexponential response. The former was explained by emission from deep donors at Ec−0.37 eV, and the latter by emission from surface states. Capture transients with stress-dependent capture barriers were also observed. An x-ray photoe...
209 citations
TL;DR: In this paper, the gate leakage currents in AlGaN/GaN heterostructure field effect transistor (HFET) structures with conventional and polarization-enhanced barriers have been studied.
Abstract: Gate leakage currents in AlGaN/GaN heterostructure field-effect transistor (HFET) structures with conventional and polarization-enhanced barriers have been studied Comparisons of extensive gate leakage current measurements with two-dimensional simulations show that vertical tunneling is the dominant mechanism for gate leakage current in the standard-barrier HFET and that the enhanced-barrier structure suppresses this mechanism in order to achieve a reduced leakage current An analytical model of vertical tunneling in a reverse-biased HFET gate-drain diode is developed to evaluate the plausibility of this conclusion The model can be fit to the measured data, but suggests that additional leakage mechanisms such as lateral tunneling from the edge of the gate to the drain or defect-assisted tunneling also contribute to the total leakage current The vertical tunneling current mechanism is shown to be more significant to the gate leakage current in III–V nitride HFETs than in HFETs fabricated in other III–V
194 citations