Effect of Buffer Layer and III/V Ratio on the Surface Morphology of Gan Grown by MBE

Piquette, E. C.; Bridger, P. M.; Beach, Robin; McGill, T. C.

doi:10.1557/proc-537-g3.77

Cited by 4 publications

(3 citation statements)

References 7 publications

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“…These studies have focused primarily on oxygen electrocatalysis, − and the two most recent reports on Pt thin films grown by PLD address the electrocatalysis of oxygen reduction. , In most cases, the crystalline properties (orientation and grain size) were characterized, but the morphological features (three-dimensional particles or flat layers) and the quality of the surface orientation and the length of the terraces have never been thoroughly investigated. It is however well established that surface configuration can vary consequently with growth conditions though the formation of facets or the occurrence of surface defects such as steps or grain boundaries. − This is of the utmost importance, since the atomic surface arrangement may differ from the bulk properties and some electrocatalytic reactions are critically dependent on the length of the terraces.…”

Section: Introductionmentioning

confidence: 99%

Pt Thin Films with Nanometer-Sized Terraces of (100) Orientation

et al. 2017

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Pulsed laser deposition was used to grow thin layers of Pt on (001)-oriented MgO substrate. The deposition temperature was varied from −25 to 600 °C, and the film thickness was varied from ca. 7 to 45 nm. The crystalline quality, orientation, and epitaxial relationship of Pt thin films on (001)-oriented MgO substrate were investigated by atomic force microscopy and X-ray diffraction as well as through electrochemical probe reactions that are sensitive to the surface crystallographic orientations (H adsorption/desorption) and the width of the (100) terrace (NH 3 electro-oxidation reaction). All thin (7 nm thick) Pt films exhibit only one diffraction peak (the (001) peak) and a 4fold in-plane symmetry, indicating epitaxial growth is achieved independently of the deposition temperature. Moreover, the pole figure indicates that all films exhibit a Pt(001)[010]//[010](001)MgO cube-on-cube epitaxial relationship, which is consistent with the AFM images. The films are prepared with nearly 60% of (100) sites, and the maximum width of the (100) terraces is nine atomic rows, attained at 325 °C.

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Section: Introductionmentioning

confidence: 99%

Pt Thin Films with Nanometer-Sized Terraces of (100) Orientation

et al. 2017

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“…It is well known that this growth condition yields very smooth surface morphology but also residual 1-lm-to 2-lm-wide Ga droplets on the sample surface. [17][18][19] The droplets were removed by etching each sample in HCl:H 2 O (1:3). Optical microscopy was used to verify that the droplets had been removed.…”

Section: Methodsmentioning

confidence: 99%

Investigation of Si and O Donor Impurities in Unintentionally Doped MBE-Grown GaN on SiC(0001) Substrate

Tingberg

Ive

Larsson

2017

Journal of Elec Materi

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We have investigated the unintentional n-type background doping in GaN(0001) layers grown on semi-insulating 4H-SiC(0001) substrate by plasma-assisted molecular beam epitaxy under Ga-rich conditions at growth temperatures from 780°C and 900°C. All layers exhibited very smooth surface morphology with monolayer steps as revealed by atomic force microscopy. Hall-effect measurements showed that the sample grown at 900°C had carrier concentration of 9.8 9 10 17 cm À3 while the sample grown at 780°C had resistivity too high to obtain reliable measurements. Secondary-ion mass spectroscopy revealed O and Si concentrations of <10 17 cm À3 in the sample grown at 900°C but >10 17 cm À3 in the sample grown at 780°C. The trend for the atomic concentrations of O and Si, which are common donor impurities in GaN, was thus contrary to the trend of the carrier concentration. The fullwidth at half-maximum for x-ray rocking curves obtained across the GaN(0002) and GaN(10 15) reflections for the sample grown at 900°C was 62 arcsec and 587 arcsec, respectively. The half-width increased with decreasing growth temperature. The atomic concentrations of O and Si are too low to account for the unintentional background doping levels. A possible explanation proposed in early reports for the background doping is N-vacancies.

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“…Following the growth of an AlN nucleation layer, a thick GaN buffer is grown to spatially separate the impurities at the regrowth interface from the HEMT channel and improve electrical isolation. Unlike other III-V materials, GaN grown by PAMBE typically needs growth conditions with a group-III/V ratio greater than 1, i.e., metal-rich conditions, 10,11 in order to achieve a smooth surface morphology.…”

Section: Introductionmentioning

confidence: 99%

Plasma-assisted Molecular Beam Epitaxy of N-polar InAlN-barrier High-electron-mobility Transistors

Hardy

Storm

Katzer

et al. 2016

JoVE

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Plasma-assisted molecular beam epitaxy is well suited for the epitaxial growth of III-nitride thin films and heterostructures with smooth, abrupt interfaces required for high-quality high-electron-mobility transistors (HEMTs). A procedure is presented for the growth of N-polar InAlN HEMTs, including wafer preparation and growth of buffer layers, the InAlN barrier layer, AlN and GaN interlayers and the GaN channel. Critical issues at each step of the process are identified, such as avoiding Ga accumulation in the GaN buffer, the role of temperature on InAlN compositional homogeneity, and the use of Ga flux during the AlN interlayer and the interrupt prior to GaN channel growth. Compositionally homogeneous N-polar InAlN thin films are demonstrated with surface root-mean-squared roughness as low as 0.19 nm and InAlN-based HEMT structures are reported having mobility as high as 1,750 cm/V∙sec for devices with a sheet charge density of 1.7 x 10 cm.

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Effect of Buffer Layer and III/V Ratio on the Surface Morphology of Gan Grown by MBE

Cited by 4 publications

References 7 publications

Pt Thin Films with Nanometer-Sized Terraces of (100) Orientation

Pt Thin Films with Nanometer-Sized Terraces of (100) Orientation

Investigation of Si and O Donor Impurities in Unintentionally Doped MBE-Grown GaN on SiC(0001) Substrate

Plasma-assisted Molecular Beam Epitaxy of N-polar InAlN-barrier High-electron-mobility Transistors

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