Observation of a two-dimensional electron gas in low pressure metalorganic chemical vapor deposited GaN-Al<i>x</i>Ga1−<i>x</i>N heterojunctions

Khan, M. Asif; Kuznia, J. N.; Hove, J. M. Van; Pan, N.; Carter, J.

doi:10.1063/1.106798

Cited by 217 publications

(85 citation statements)

References 17 publications

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“…material quality, the effect has only been produced in a handful of materials, with each of them exhibiting distinctive features in the QH regime as a result of their peculiar electronic properties 5,[7][8][9][10][11] .…”

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confidence: 99%

“…The high mobility enable us, for the first time, to observe the QH effect in black Page 4 of 15 phosphorus 2DEG. Black phosphorus thus joins the selected few materials 5,7,8,11 to become the only 2D atomic crystal apart from graphene 9,10 having requisite material quality to show QH effect.We constructed the van der Waals heterostructure using the dry-transfer technique described in ref. 31.…”

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confidence: 99%

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Quantum Hall effect in black phosphorus two-dimensional electron system

et al. 2016

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Development of new, high quality functional materials has been at the forefront of condensed matter research. The recent advent of two-dimensional black phosphorus has greatly enriched the material base of two-dimensional electron systems.Significant progress has been made to achieve high mobility black phosphorus twodimensional electron gas (2DEG) since the development of the first black phosphorus field-effect transistors (FETs) [1][2][3][4] . Here, we reach a milestone in developing high quality black phosphorus 2DEG -the observation of integer quantum Hall (QH) effect. We achieve high quality by embedding the black phosphorus 2DEG in a van der Waals heterostructure close to a graphite back gate; the graphite gate screens the impurity potential in the 2DEG, and brings the carrier Hall mobility up to 6000. The exceptional mobility enabled us, for the first time, to observe QH effect, and to gain important information on the energetics of the spin-split Landau levels in black phosphorus. Our results set the stage for further study on quantum transport and device application in the ultrahigh mobility regime.Quantum Hall effect, the emergence of quantized Hall resistance in 2DEG sample when subjected to low temperatures and strong magnetic fields, has had a lasting impact in modern condensed matter research. The exact, universal quantization regardless of detailed sample geometry and impurity configuration has enabled the establishment of a metrological resistance standard, and served as the basis for an independent determination of the fine structure constant 5 . Even though the exact quantization of the Hall resistance relies on certain amount of impurities 6 , the observation of QH effect, paradoxically, requires high-purity, low-defect specimens. Because of the stringent requirement on the ). In this work, we achieved high Hall mobility in black phosphorus FETs that is significantly higher than previous record value. This is accomplished by constructing a van der Waals heterostructure with the few-layer black phosphorus sandwiched between two hBN flakes (Fig. 1a,b) and placed on graphite back gate. The top hBN protects the black phosphorus flakes from sample degradation in air. More importantly, the thin bottom hBN (thickness ~ 25 nm) allows the electrons in the graphite to screen the impurity potential at the black phosphorus-hBN interface, where the 2DEG resides. The high mobility enable us, for the first time, to observe the QH effect in black Page 4 of 15 phosphorus 2DEG. Black phosphorus thus joins the selected few materials 5,7,8,11 to become the only 2D atomic crystal apart from graphene 9,10 having requisite material quality to show QH effect.We constructed the van der Waals heterostructure using the dry-transfer technique described in ref. 31. We first cleaved graphite and h-BN flakes onto SiO2/Si wafers, and black phosphorus flake onto poly-propylene carbon (PPC) film. The black phosphorus flake on the PPC film was then used to pick up the h-BN flake on the SiO2/Si wafer. Finally, the black phosphor...

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Quantum Hall effect in black phosphorus two-dimensional electron system

et al. 2016

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“…Since the first demonstration of the existence of a twodimensional electron gas ͑2DEG͒ at the AlGaN/GaN interface in 1992, 1 tremendous progress has been realized 2 in the field of AlGaN/GaN high electron mobility transistors deposited on various substrates by different growth techniques. For example, Gaska et al 3 reached a room-temperature mobility slightly over 2000 cm 2 /V s (n s ϭ1.3ϫ10 12 cm Ϫ2 ) in an Al 0.2 Ga 0.8 N/GaN structure deposited on 6H-SiC substrate by low-pressure metalorganic vapor-phase epitaxy.…”

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High electron mobility in AlGaN/GaN heterostructures grown on bulk GaN substrates

Frayssinet

Knap

Lorenzini

et al. 2000

Applied Physics Letters

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129

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Dislocation-free high-quality AlGaN/GaN heterostructures have been grown by molecular-beam epitaxy on semi-insulating bulk GaN substrates. Hall measurements performed in the 300 K–50 mK range show a low-temperature electron mobility exceeding 60 000 cm2/V s for an electron sheet density of 2.4×1012 cm−2. Magnetotransport experiments performed up to 15 T exhibit well-defined quantum Hall-effect features. The structures corresponding to the cyclotron and spin splitting were clearly resolved. From an analysis of the Shubnikov de Hass oscillations and the low-temperature mobility we found the quantum and transport scattering times to be 0.4 and 8.2 ps, respectively. The high ratio of the scattering to quantum relaxation time indicates that the main scattering mechanisms, at low temperatures, are due to long-range potentials, such as Coulomb potentials of ionized impurities.

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“…In 1992, M. Asif Khan et al first reported the observation of a two-dimensional electron gas (2DEG) in MOCVD-grown AlGaN/GaN heterojections with promising electron properties [3]. This news together with the simulation results [4] that predict high peak velocity, high saturation velocity, and high electron mobility in GaN started to make the AlGaN/GaN heterostructures attractive for microwave and millimeterwave devices and thus to spur more investigations to see its potential.…”

Section: Pappermentioning

confidence: 99%

“…In 1992, Asif Kahn et al reported the first confirmation of high-mobility twodimensional electron gas forming in the Ga-face Al x Ga 1-x N/GaN heterostructure [3], which serves as the basis of the epitaxial structure for high electron mobility transistors (HEMTs). Since then, the growth of AlGaN/GaN HEMT epitaxial structures has been intensively studied and advanced on various substrates, including sapphire, SiC, Si and bulk GaN substrates, using growth techniques such as molecular beam epitaxy (MBE) or metalorganic chemical vapor deposition (MOCVD).…”

Section: Epitaxial Structuresmentioning

confidence: 99%

MOCVD growth of GaN-based high electron mobility transistor structures

Chen¹

2015

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IICover: surface morphology of a GaN high electron mobility transistor structure grown on a native GaN substrate. The image was obtained with an atomic force microscope. AbstractWide bandgap group-III nitride semiconductors like GaN, AlN, and their alloys are very suitable for the use in high-power, high-frequency electronics, as a result of their superior intrinsic properties. The polarization-induced high-density and high-mobility two-dimensional electron gas (2DEG) forming in (0001) oriented AlGaN/GaN heterostructures enable the epitaxial structure to be utilized for high electron mobility transistors (HEMTs). Outstanding power handling and record high frequency have been demonstrated from GaN-based HEMT devices over time. However, the shortterm stability and the long-term reliability of the device performances remain problematic. In order to make GaN HEMT technology truly take off and breach the civilian market like automotive, telecommunication applications, the problems need to be solved to justify its relatively high cost over the solutions based on Si and GaAs technologies.At the material level, there are two major challenges; one is the reduction of highdensity structural defects in heteroepitaxially grown layers when foreign substrates are used, and the other is the control of "deep" electron traps forming in the middle of the "wide" bandgap by intrinsic defects or extrinsic impurities.The main idea of the present work was therefore to tackle these material issues directly, using an approach called bottom-to-top optimization to improve the overall quality of GaN-based HEMT epitaxial structures grown on semi-insulating (SI) SiC and native GaN substrates. The bottom-to-top optimization means an entire growth process optimization, from in-situ substrate pretreatment to the epitaxial growth and then the cooling process. Great effort was put to gain the understanding of the influence of growth parameters on material properties and consequently to establish an advanced and reproducible growth process. Many state-of-the-art material properties of GaNbased HEMT structures were achieved in this work, including superior structural integrity of AlN nucleation layers for ultra-low thermal boundary resistance, excellent control of residual impurities, outstanding and nearly-perfect crystalline quality of GaN epilayers grown on SiC and native GaN substrates, respectively, and record-high room temperature 2DEG mobility obtained in simple AlGaN/GaN heterostructures.The epitaxial growth of the wide bandgap III-nitride epilayers like GaN, AlN, AlGaN, and InAlN, as well as various GaN-based HEMT structures was all carried out in a hot-wall metalorganic chemical vapor deposition (MOCVD) system. A variety of structural and electrical characterizations were routinely used to provide fast feedback VI for adjusting growth parameters and developing improved growth processes, such as optical microscopy (OM), atomic force microscopy (AFM), x-ray diffraction (XRD), capacitance-voltage measurement (CV) as well as sheet resistance...

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Observation of a two-dimensional electron gas in low pressure metalorganic chemical vapor deposited GaN-AlxGa1−xN heterojunctions

Cited by 217 publications

References 17 publications

Quantum Hall effect in black phosphorus two-dimensional electron system

Quantum Hall effect in black phosphorus two-dimensional electron system

High electron mobility in AlGaN/GaN heterostructures grown on bulk GaN substrates

MOCVD growth of GaN-based high electron mobility transistor structures

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