Novel dielectrics for gate oxides and surface passivation on GaN

Gila, B. P.; Thaler, G. T.; Onstine, A. H.; Hlad, M.; Gerger, Andrew; Herrero, Andrew M.; Allums, K. K.; Stodilka, D.; Jang, Soohwan; Kang, B. S.; Anderson, Travis J.; Abernathy, C. R.; Ren, F.; Pearton, S. J.

doi:10.1016/j.sse.2006.04.001

Cited by 33 publications

(13 citation statements)

References 35 publications

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“…Preparing gate and passivation oxides on GaN surfaces remains an important challenge, and provides a context in which the value of a smooth CaO morphology can be estimated 40 . The CaO capacitors have a constant dielectric thickness of 4.5 nm and a Dy 2 O 3 cap thickness of 0.8 nm.…”

Section: Discussionmentioning

confidence: 99%

Surfactant-enabled epitaxy through control of growth mode with chemical boundary conditions

et al. 2011

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Property coupling at interfaces between active materials is a rich source of functionality, if defect densities are low, interfaces are smooth and the microstructure is featureless. Conventional synthesis techniques generally fail to achieve this when materials have highly dissimilar structure, symmetry and bond type-precisely when the potential for property engineering is most pronounced. Here we present a general synthesis methodology, involving systematic control of the chemical boundary conditions in situ, by which the crystal habit, and thus growth mode, can be actively engineered. In so doing, we establish the capability for layer-by-layer deposition in systems that otherwise default to island formation and grainy morphology. This technique is demonstrated via atomically smooth {111} calcium oxide films on (0001) gallium nitride. The operative surfactant-based mechanism is verified by temperature-dependent predictions from ab initio thermodynamic calculations. Calcium oxide films with smooth morphology exhibit a three order of magnitude enhancement of insulation resistance.

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Section: Discussionmentioning

confidence: 99%

Surfactant-enabled epitaxy through control of growth mode with chemical boundary conditions

et al. 2011

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“…Although MgO and CaO are immiscible with each other below 2000 °C, previous reports , have shown that Mg x Ca 1– x O can be grown by MBE at lower temperature without phase separation. In order to examine the microscopic crystallinity and phase composition of the Mg x Ca 1– x O films deposited by this ALD method, transmission electron microscopy (TEM) was employed.…”

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confidence: 93%

Epitaxial Growth of Mg_xCa_1–xO on GaN by Atomic Layer Deposition

et al. 2016

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Abstract:We demonstrate for the first time that a single-crystalline epitaxial Si-based power devices could not meet these demands due to the small band gap (1.1 eV) and low breakdown field of Si. 2 GaN could replace Si for future power applications because of its higher band gap (3.4eV) and higher breakdown field. One powerful method to examine the epitaxial film quality is cross-sectional TEM imaging. GaN. The well-defined film spots in the diffraction pattern (Fig. S2) peaks are seen in all three samples (Fig. 3 a). The absence of MgO and CaO peaks indicates that phase separation into the two binaries has not occurred. The A "top-to-top" capacitor structure was used to measure the capacitance due to the insulating sapphire substrate under the GaN (Fig. S3). In this measurement, the positive probe is placed in contact with the gate electrode while the negative probe is in contact with the large area of GaN covered by aluminum metal. Since the gate has a serial connection with the large area, the measured capacitance is given by, where m C is the capacitance measured by the LCR meter, g C is the capacitance of the gate and l C is the capacitance of the larger area. Since C l >> C g , the measured capacitance is dominated by the gate: m g C C .The measured room temperature and high temperature CV curves from three Mg x Ca 1-x O /GaN samples as well as an Al 2 O 3 /GaN sample are summarized in Fig. 4.In room temperature studies (Fig. 4 a, b and c there is a 20% dispersion in the same region in the Al 2 O 3 /GaN sample (Fig. 4 d) 20 The detailed measurement procedure and conductance data are summarized in the supporting information (Fig. S5). 18 The measured values of D it are summarized in Fig. 4 i. Two of the samples with epitaxial films show the lowest D it

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“…Relative to the vast wet chemical reaction sequences available for group IV semiconductor surfaces, − there are comparatively few established wet chemical methodologies for modifying the native surfaces of GaAs and GaN. − The most effective and most common type of wet chemical reactions for functionalizing GaAs and GaN surfaces involves immersion in solutions with sulfur-containing reagents (e.g., Na 2 S or alkanethiols), − affecting the observable wetting properties, the surface energetics (i.e., the conduction and valence band edge electrochemical potentials), and/or surface charge trap density. − Although a comprehensive analysis of thiol/sulfide treatments is outside the scope of this report, the main conclusions to be drawn from decades of research are that these wet chemical strategies were not designed from a detailed molecular-level understanding of surface reactivity and are accordingly not adequate in many optoelectronic applications. For example, thiol-based treatments are inferior to epitaxial surface capping layers (e.g., Al x Ga 1– x As, SiN x ) − for ameliorating surface defects long-term. To determine whether any wet chemical strategy for III–V surfaces can supplant costly and complex solid-state surface treatments, better insight on the wet chemical reactivity of these semiconductor interfaces is needed.…”

Section: Introductionmentioning

confidence: 99%

Wet Chemical Functionalization of III–V Semiconductor Surfaces: Alkylation of Gallium Arsenide and Gallium Nitride by a Grignard Reaction Sequence

et al. 2012

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Crystalline gallium arsenide (GaAs) (111)A and gallium nitride (GaN) (0001) surfaces have been functionalized with alkyl groups via a sequential wet chemical chlorine activation, Grignard reaction process. For GaAs(111)A, etching in HCl in diethyl ether effected both oxide removal and surface-bound Cl. X-ray photoelectron (XP) spectra demonstrated selective surface chlorination after exposure to 2 M HCl in diethyl ether for freshly etched GaAs(111)A but not GaAs(111)B surfaces. GaN(0001) surfaces exposed to PCl(5) in chlorobenzene showed reproducible XP spectroscopic evidence for Cl-termination. The Cl-activated GaAs(111)A and GaN(0001) surfaces were both reactive toward alkyl Grignard reagents, with pronounced decreases in detectable Cl signal as measured by XP spectroscopy. Sessile contact angle measurements between water and GaAs(111)A interfaces after various levels of treatment showed that GaAs(111)A surfaces became significantly more hydrophobic following reaction with C(n)H(2n-1)MgCl (n = 1, 2, 4, 8, 14, 18). High-resolution As 3d XP spectra taken at various times during prolonged direct exposure to ambient lab air indicated that the resistance of GaAs(111)A to surface oxidation was greatly enhanced after reaction with Grignard reagents. GaAs(111)A surfaces terminated with C(18)H(37) groups were also used in Schottky heterojunctions with Hg. These heterojunctions exhibited better stability over repeated cycling than heterojunctions based on GaAs(111)A modified with C(18)H(37)S groups. Raman spectra were separately collected that suggested electronic passivation by surficial Ga-C bonds at GaAs(111)A. Specifically, GaAs(111)A surfaces reacted with alkyl Grignard reagents exhibited Raman signatures comparable to those of samples treated with 10% Na(2)S in tert-butanol. For GaN(0001), high-resolution C 1s spectra exhibited the characteristic low binding energy shoulder demonstrative of surface Ga-C bonds following reaction with CH(3)MgCl. In addition, 4-fluorophenyl groups were attached and detected after reaction with C(6)H(4)FMgBr, further confirming the susceptibility of Cl-terminated GaN(0001) to surface alkylation. However, the measured hydrophobicities of alkyl-terminated GaAs(111)A and GaN(0001) were markedly distinct, indicating differences in the resultant surface layers. The results presented here, in conjunction with previous studies on GaP, show that atop Ga atoms at these crystallographically related surfaces can be deliberately functionalized and protected through Ga-C surface bonds that do not involve thiol/sulfide chemistry or gas-phase pretreatments.

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Novel dielectrics for gate oxides and surface passivation on GaN

Cited by 33 publications

References 35 publications

Surfactant-enabled epitaxy through control of growth mode with chemical boundary conditions

Surfactant-enabled epitaxy through control of growth mode with chemical boundary conditions

Epitaxial Growth of Mg_xCa_1–xO on GaN by Atomic Layer Deposition

Wet Chemical Functionalization of III–V Semiconductor Surfaces: Alkylation of Gallium Arsenide and Gallium Nitride by a Grignard Reaction Sequence

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Novel dielectrics for gate oxides and surface passivation on GaN

Cited by 33 publications

References 35 publications

Surfactant-enabled epitaxy through control of growth mode with chemical boundary conditions

Surfactant-enabled epitaxy through control of growth mode with chemical boundary conditions

Epitaxial Growth of MgxCa1–xO on GaN by Atomic Layer Deposition

Wet Chemical Functionalization of III–V Semiconductor Surfaces: Alkylation of Gallium Arsenide and Gallium Nitride by a Grignard Reaction Sequence

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Epitaxial Growth of Mg_xCa_1–xO on GaN by Atomic Layer Deposition