The Experts below are selected from a list of 315 Experts worldwide ranked by ideXlab platform
Kevin J Chen - One of the best experts on this subject based on the ideXlab platform.
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interface border trap characterization of al2o3 aln gan metal oxide semiconductor structures with an aln interfacial layer
Applied Physics Letters, 2015Co-Authors: Shenghou Liu, Shu Yang, Zhikai Tang, Qimeng Jiang, Cheng Liu, Maojun Wang, Bo Shen, Kevin J ChenAbstract:We report the interface characterization of Al2O3/AlN/GaN MOS (metal-oxide-semiconductor) structures with an AlN interfacial layer. A thin monocrystal-like interfacial layer (AlN) is formed at the Al2O3/GaN to effectively block oxygen from the GaN surface and prevent the formation of detrimental Ga-O bonds. The suppression of Ga-O bonds is validated by X-ray photoelectron spectroscopy of the critical interface. Frequency-dispersion in C-V characteristics has been significantly reduced, owing to improved interface quality. Furthermore, using the conventional conductance method suitable for extracting the interface trap density Dit in MOS structures, Dit in the device with AlN was determined to be in the range of 1011–1012 eV−1 cm−2, showing one order of magnitude lower than that without AlN. Border traps near the gate-dielectric/GaN interface were identified and shown to be suppressed by the AlN interfacial layer as well.
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mechanism of peald grown aln passivation for algan gan hemts compensation of interface traps by polarization charges
IEEE Electron Device Letters, 2013Co-Authors: Sen Huang, Shu Yang, Zhikai Tang, Qimeng Jiang, Kevin J ChenAbstract:The physical mechanism of passivation of AlGaN/GaN HEMTs by AlN thin film prepared with plasma-enhanced atomic layer deposition (PEALD) is investigated by characterizing Ni- Al2O3/AlN-GaN/AlGaN/GaN metal-insulator-semiconductor (MIS) diodes. The dielectric stack Al2O3/AlN (13/2 nm) exhibits similar capability in suppressing the current collapse in AlGaN/GaN HEMTs as the 4-nm PEALD-AlN thin film used in our previous work but delivers much lower vertical leakage to facilitate the capacitance-voltage characterizations. Exceptionally large negative bias (<; -8 V) is required to deplete the 2-D electron gas in the MIS diode's C-V measurement. By virtue of quasi-static C-V characterization, it is revealed that positive fixed charges of ~ 3.2 × 1013 e/cm2 are introduced by the PEALD-AlN. The positive fixed charges are suggested to be polarization charges in the monocrystal-like PEALD-AlN. They can effectively compensate the high-density slow-response acceptor-like interface traps, resulting in effective suppression of current collapse.
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effective passivation of algan gan hemts by ald grown aln thin film
IEEE Electron Device Letters, 2012Co-Authors: Sen Huang, Shu Yang, Qimeng Jiang, Chunhua Zhou, Kevin J ChenAbstract:An effective passivation technique for AlGaN/GaN high-electron-mobility transistors (HEMTs) is presented. This technique features an AlN thin film grown by plasma-enhanced atomic layer deposition (PEALD). With in situ remote plasma pretreatments prior to the AlN deposition, an atomically sharp interface between ALD-AlN and III-nitride has been obtained. Significant current collapse suppression and dynamic ON-resistance reduction are demonstrated in the ALD-AlN-passivated AlGaN/GaN HEMTs under high-drain-bias switching conditions.
Hadis Morkoç - One of the best experts on this subject based on the ideXlab platform.
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the effect of aln interlayer thicknesses on scattering processes in lattice matched alinn gan two dimensional electron gas heterostructures
New Journal of Physics, 2009Co-Authors: A Teke, Hadis Morkoç, S Gokden, R Tulek, J H Leach, U Ozgur, S B Lisesivdin, Ekmel OzbayAbstract:The scattering mechanisms governing the transport properties of high mobility AlInN/AlN/GaN two-dimensional electron gas (2DEG) heterostructures with various AIN spacer layer thicknesses from zero to 2 nm were presented. The major scattering processes including acoustic and optical phonons, ionized impurity, interface roughness, dislocation and alloy disorder were applied to the temperature-dependent mobility data. It was found that scattering due mainly to alloy disorder limits the electron mobility for samples having spacer layer thicknesses up to 0.3 nm. On the other hand, alloy scattering is greatly reduced as the AlN spacer layer thickness increases further, and hence the combination of acoustic, optical and interface roughness become operative with different degrees of effectiveness over different temperature ranges. The room-temperature electron mobility was observed to increase gradually as the AlN spacer layer increases. A peak electron mobility of 1630 cm2 V−1 s−1 was realized for the sample consisting of a 1 nm AlN spacer layer. Then, the electron mobility decreased for the sample with 2 nm AlN. Moreover, the measured 2DEG densities were also compared with the theoretical predictions, which include both piezoelectric and spontaneous polarization components existing at AlN/GaN interfaces. The experimental sheet carrier densities for all AlInN/AlN/GaN HEMT structures were found to be in excellent agreement with the theoretical predictions when the parasitic (unintentional) GaN layer deposited between AlN and AlInN was taken into account. From these analyses, 1 nm AlN spacer layer thickness is found to be the optimum thickness required for high electron mobility and hence low sheet resistance once the sheet carrier density is increased to the theoretically expected value for the sample without unintentional GaN layer.
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valence band discontinuities of wurtzite gan aln and inn heterojunctions measured by x ray photoemission spectroscopy
Applied Physics Letters, 1996Co-Authors: G. Martin, A Botchkarev, Angus Rockett, Hadis MorkoçAbstract:The valence‐band discontinuities at various wurtzite GaN, AlN, and InN heterojunctions were measured by means of x‐ray photoemission spectroscopy. A significant forward–backward asymmetry was observed in the InN/GaN–GaN/InN and InN/AlN–AlN/InN heterojunctions. The asymmetry was understood as a piezoelectric strain effect. We report the valence band discontinuities for InN/GaN=1.05±0.25 eV, GaN/AlN=0.70±0.24 eV, and InN/AlN=1.81±0.20 eV, all in the standard type I lineup. These values obey transitivity to within the experimental accuracy. Tables of photoemission core level binding energies are reported for wurtzite GaN, AlN, and InN.
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valence band discontinuity between gan and aln measured by x ray photoemission spectroscopy
Applied Physics Letters, 1994Co-Authors: G. Martin, R.l. W. Lambrecht, A Botchkarev, Hadis Morkoç, Angus Rockett, Arvind Agarwal, S. Strite, B SegallAbstract:The valence‐band discontinuity at a wurtzite GaN/AlN(0001) heterojunction is measured by x‐ray photoemission spectroscopy. The method first measures the core level binding energies with respect to the valence‐band maximum in both GaN and AlN bulk films. The precise location of the valence‐band maximum is determined by aligning prominent features in the valence‐band spectrum with calculated densities of states. Tables of core level binding energies relative to the valence‐band maximum are reported for both GaN and AlN. Subsequent measurements of separations between Ga and Al core levels for thin overlayers of GaN film grown on AlN and vice versa yield a valence‐band discontinuity of ΔEV=0.8±0.3 eV in the standard type I heterojunction alignment.
James S Speck - One of the best experts on this subject based on the ideXlab platform.
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correlation between threading dislocation density and sheet resistance of algan aln gan heterostructures grown by plasma assisted molecular beam epitaxy
Applied Physics Letters, 2012Co-Authors: Stephen W Kaun, Man Hoi Wong, U K Mishra, James S SpeckAbstract:AlGaN/AlN/GaN heterostructures were grown on 6H-SiC, GaN-on-sapphire, and free-standing GaN, resulting in heterostructures with threading dislocation densities of ∼2 × 1010, ∼5 × 108, and ∼5 × 107 cm−2, respectively. Growths were carried out under Ga-rich conditions by plasma-assisted molecular beam epitaxy to determine the influence of threading dislocation density on the sheet resistance of AlGaN/AlN/GaN heterostructures. High threading dislocation density was observed to significantly degrade Hall mobility. An AlGaN/AlN/GaN heterostructure with a ∼2 nm AlN interlayer and a threading dislocation density of ∼5 × 107 cm−2 achieved the very low room temperature sheet resistance of 175 Ω/□.
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aln gan and al ga n aln gan two dimensional electron gas structures grown by plasma assisted molecular beam epitaxy
Journal of Applied Physics, 2001Co-Authors: I P Smorchkova, James S Speck, L F Chen, Tom Mates, L Shen, S Heikman, B Moran, Stacia Keller, Steven P Denbaars, U K MishraAbstract:We report on an extensive study of the two-dimensional electron gas (2DEG) structures containing AlN layers. It is shown that the presence of large polarization fields in the AlN barrier layer in AlN/GaN heterostructures results in high values of the 2DEG sheet density of up to 3.6×1013 cm−2. Room-temperature sheet resistance of 180 Ω/□ is demonstrated in the AlN/GaN structure with a 35 A AlN barrier. As a result of reduced alloy disorder scattering, low-temperature electron mobility is significantly enhanced in AlN/GaN heterostructures in comparison to AlGaN/GaN structures with similar values of the 2DEG sheet density. The growth of GaN cap layers on top of AlN/GaN structures with relatively thick (∼35 A) AlN barriers is found to lead to a significant decrease in the 2DEG sheet density. However, inserting a thin (∼10 A) AlN layer between AlxGa1−xN and GaN in the AlxGa1−xN/GaN (x∼0.2–0.45) 2DEG structures does not affect the 2DEG sheet density and results in an increase of the low-temperature electron mob...
G. Martin - One of the best experts on this subject based on the ideXlab platform.
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valence band discontinuities of wurtzite gan aln and inn heterojunctions measured by x ray photoemission spectroscopy
Applied Physics Letters, 1996Co-Authors: G. Martin, A Botchkarev, Angus Rockett, Hadis MorkoçAbstract:The valence‐band discontinuities at various wurtzite GaN, AlN, and InN heterojunctions were measured by means of x‐ray photoemission spectroscopy. A significant forward–backward asymmetry was observed in the InN/GaN–GaN/InN and InN/AlN–AlN/InN heterojunctions. The asymmetry was understood as a piezoelectric strain effect. We report the valence band discontinuities for InN/GaN=1.05±0.25 eV, GaN/AlN=0.70±0.24 eV, and InN/AlN=1.81±0.20 eV, all in the standard type I lineup. These values obey transitivity to within the experimental accuracy. Tables of photoemission core level binding energies are reported for wurtzite GaN, AlN, and InN.
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valence band discontinuity between gan and aln measured by x ray photoemission spectroscopy
Applied Physics Letters, 1994Co-Authors: G. Martin, R.l. W. Lambrecht, A Botchkarev, Hadis Morkoç, Angus Rockett, Arvind Agarwal, S. Strite, B SegallAbstract:The valence‐band discontinuity at a wurtzite GaN/AlN(0001) heterojunction is measured by x‐ray photoemission spectroscopy. The method first measures the core level binding energies with respect to the valence‐band maximum in both GaN and AlN bulk films. The precise location of the valence‐band maximum is determined by aligning prominent features in the valence‐band spectrum with calculated densities of states. Tables of core level binding energies relative to the valence‐band maximum are reported for both GaN and AlN. Subsequent measurements of separations between Ga and Al core levels for thin overlayers of GaN film grown on AlN and vice versa yield a valence‐band discontinuity of ΔEV=0.8±0.3 eV in the standard type I heterojunction alignment.
Shengjun Zhou - One of the best experts on this subject based on the ideXlab platform.
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effect of strain relaxation on performance of ingan gan green leds grown on 4 inch sapphire substrate with sputtered aln nucleation layer
Scientific Reports, 2019Co-Authors: Shengjun Zhou, Hui Wan, Xingtong LiuAbstract:Here we demonstrate high-brightness InGaN/GaN green light emitting diodes (LEDs) with in-situ low-temperature GaN (LT-GaN) nucleation layer (NL) and ex-situ sputtered AlN NL on 4-inch patterned sapphire substrate. Compared to green LEDs on LT-GaN (19 nm)/sapphire template, green LEDs on sputtered AlN (19 nm)/template has better crystal quality while larger in-plane compressive strain. As a result, the external quantum efficiency (EQE) of green LEDs on sputtered AlN (19 nm)/sapphire template is lower than that of green LEDs on LT-GaN (19 nm)/sapphire template due to strain-induced quantum-confined Stark effect (QCSE). We show that the in-plane compressive strain of green LEDs on sputtered AlN/sapphire templates can be manipulated by changing thickness of the sputtered AlN NL. As the thickness of sputtered AlN NL changes from 19 nm to 40 nm, the green LED on sputtered AlN (33 nm)/sapphire template exhibits the lowest in-plane compressive stress and the highest EQE. At 20 A/cm2, the EQE of 526 nm green LEDs on sputtered AlN (33 nm)/sapphire template is 36.4%, about 6.1% larger than that of the green LED on LT-GaN (19 nm)/sapphire template. Our experimental data suggest that high-efficiency green LEDs can be realized by growing InGaN/GaN multiple quantum wells (MQWs) on sputtered AlN/sapphire template with reduced in-plane compressive strain and improved crystal quality.
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Effect of strain relaxation on performance of InGaN/GaN green LEDs grown on 4-inch sapphire substrate with sputtered AlN nucleation layer
Nature Publishing Group, 2019Co-Authors: Shengjun Zhou, Hui Wan, Xingtong LiuAbstract:Abstract Here we demonstrate high-brightness InGaN/GaN green light emitting diodes (LEDs) with in-situ low-temperature GaN (LT-GaN) nucleation layer (NL) and ex-situ sputtered AlN NL on 4-inch patterned sapphire substrate. Compared to green LEDs on LT-GaN (19 nm)/sapphire template, green LEDs on sputtered AlN (19 nm)/template has better crystal quality while larger in-plane compressive strain. As a result, the external quantum efficiency (EQE) of green LEDs on sputtered AlN (19 nm)/sapphire template is lower than that of green LEDs on LT-GaN (19 nm)/sapphire template due to strain-induced quantum-confined Stark effect (QCSE). We show that the in-plane compressive strain of green LEDs on sputtered AlN/sapphire templates can be manipulated by changing thickness of the sputtered AlN NL. As the thickness of sputtered AlN NL changes from 19 nm to 40 nm, the green LED on sputtered AlN (33 nm)/sapphire template exhibits the lowest in-plane compressive stress and the highest EQE. At 20 A/cm2, the EQE of 526 nm green LEDs on sputtered AlN (33 nm)/sapphire template is 36.4%, about 6.1% larger than that of the green LED on LT-GaN (19 nm)/sapphire template. Our experimental data suggest that high-efficiency green LEDs can be realized by growing InGaN/GaN multiple quantum wells (MQWs) on sputtered AlN/sapphire template with reduced in-plane compressive strain and improved crystal quality
