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Title: Effect of epitaxial temperature on N-polar InN films grown by molecular beam epitaxy

Abstract

Effect of growth temperature on 2.3 {mu}m thick N-polar InN films grown on GaN template at 440-620 deg. C by plasma-assisted molecular beam epitaxy was investigated. We found different growth behaviors depending on the growth temperatures, which greatly influenced surface morphology. The surface showed dendritic morphologies at temperatures lower than 540 deg. C while step-flow-like morphologies and spiral growth were clearly observed at temperatures higher than 540 deg. C. Crystalline quality was improved with increasing growth temperature up to 540 deg. C and was almost saturated at higher temperatures. A gradual blueshift of the emission peak was observed from 13 K photoluminescence (PL) spectra with increasing growth temperature, which was due to the increased compressive strain in InN films. A Poisson ratio ({nu}=0.21{+-}0.05) for InN and a slope of PL peak energy as a function of {epsilon}{sub c} ({delta}E/{delta}{epsilon}{sub c}=18.9 eV) were obtained. Our results indicated that the epitaxial temperatures of 540-600 deg. C were best to achieve high quality InN films with a smooth surface.

Authors:
; ; ;  [1];  [2];  [2]
  1. Department of Electronics and Mechanical Engineering, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522 (Japan)
  2. (Japan)
Publication Date:
OSTI Identifier:
20788018
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 99; Journal Issue: 7; Other Information: DOI: 10.1063/1.2190720; (c) 2006 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; CRYSTAL GROWTH; EV RANGE 10-100; GALLIUM NITRIDES; INDIUM NITRIDES; LAYERS; MOLECULAR BEAM EPITAXY; MORPHOLOGY; PHOTOLUMINESCENCE; PLASMA; POISSON RATIO; SEMICONDUCTOR MATERIALS; SPECTRAL SHIFT; STRAINS; STRESSES; TEMPERATURE DEPENDENCE; TEMPERATURE RANGE 0400-1000 K; THIN FILMS

Citation Formats

Wang Xinqiang, Che, Song-Bek, Ishitani, Yoshihiro, Yoshikawa, Akihiko, Center for Frontier Electronics and Photonics, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, and and InN-Project as a CREST Program of JST, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522. Effect of epitaxial temperature on N-polar InN films grown by molecular beam epitaxy. United States: N. p., 2006. Web. doi:10.1063/1.2190720.
Wang Xinqiang, Che, Song-Bek, Ishitani, Yoshihiro, Yoshikawa, Akihiko, Center for Frontier Electronics and Photonics, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, & and InN-Project as a CREST Program of JST, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522. Effect of epitaxial temperature on N-polar InN films grown by molecular beam epitaxy. United States. doi:10.1063/1.2190720.
Wang Xinqiang, Che, Song-Bek, Ishitani, Yoshihiro, Yoshikawa, Akihiko, Center for Frontier Electronics and Photonics, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, and and InN-Project as a CREST Program of JST, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522. Sat . "Effect of epitaxial temperature on N-polar InN films grown by molecular beam epitaxy". United States. doi:10.1063/1.2190720.
@article{osti_20788018,
title = {Effect of epitaxial temperature on N-polar InN films grown by molecular beam epitaxy},
author = {Wang Xinqiang and Che, Song-Bek and Ishitani, Yoshihiro and Yoshikawa, Akihiko and Center for Frontier Electronics and Photonics, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522 and and InN-Project as a CREST Program of JST, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522},
abstractNote = {Effect of growth temperature on 2.3 {mu}m thick N-polar InN films grown on GaN template at 440-620 deg. C by plasma-assisted molecular beam epitaxy was investigated. We found different growth behaviors depending on the growth temperatures, which greatly influenced surface morphology. The surface showed dendritic morphologies at temperatures lower than 540 deg. C while step-flow-like morphologies and spiral growth were clearly observed at temperatures higher than 540 deg. C. Crystalline quality was improved with increasing growth temperature up to 540 deg. C and was almost saturated at higher temperatures. A gradual blueshift of the emission peak was observed from 13 K photoluminescence (PL) spectra with increasing growth temperature, which was due to the increased compressive strain in InN films. A Poisson ratio ({nu}=0.21{+-}0.05) for InN and a slope of PL peak energy as a function of {epsilon}{sub c} ({delta}E/{delta}{epsilon}{sub c}=18.9 eV) were obtained. Our results indicated that the epitaxial temperatures of 540-600 deg. C were best to achieve high quality InN films with a smooth surface.},
doi = {10.1063/1.2190720},
journal = {Journal of Applied Physics},
number = 7,
volume = 99,
place = {United States},
year = {Sat Apr 01 00:00:00 EST 2006},
month = {Sat Apr 01 00:00:00 EST 2006}
}
  • We explore the effect of growth kinetics on the structural properties of In-polar InN films on GaN templates grown near the thermal dissociation limit by plasma-assisted molecular beam epitaxy. Unlike the common growth temperature limit (T Almost-Equal-To 500 Degree-Sign C) for In-polar InN grown under In-rich conditions, slightly N-rich conditions are demonstrated to shift the available growth temperature window to much higher temperatures (by >50 Degree-Sign C). InN films grown in this high-T/N-rich regime show significantly reduced off-axis X-ray diffraction rocking curve peak widths and record low threading dislocation densities (TDD {approx} 4 Multiplication-Sign 10{sup 9} cm{sup -2}) even formore » film thicknesses <1 {mu}m, as compared to state of the art In-rich growth. The reduction of TDD is attributed to more effective TD inclination and annihilation under N-rich growth, delineating prospective routes for improved InN-based materials.« less
  • The polarity type, surface morphology, electrical properties, and deep trap spectra were studied for undoped Al{sub x}Ga{sub 1-x}N films (x=0-0.6) grown by molecular beam epitaxy on on-axis (0001) sapphire using composite buffers consisting of low temperature (LT) AlN nucleation layer, AlN, and AlN/AlGaN superlattice. It is shown that the films grow with N-polarity if the LT AlN layer is deposited under N-rich conditions and with Ga-polarity for the LT AlN layers deposited under Al-rich conditions. For both polarities the film morphology was acceptable for fabrication of typical GaN-based devices. It is demonstrated that the Ga-polar AlGaN films are heavily compensatedmore » p-type, with the dominant acceptors believed to be due to C. N-polar films are n type, with the residual donors pinning the Fermi level being most likely due to Si. N-polar films show a high concentration of deep electron traps.« less
  • We report the surface, structural, and optical properties of typical Ga- and N-polar GaN films grown on sapphire substrates by molecular beam epitaxy. The Ga-polar films were grown on AlN buffer while the N-polar films were grown on GaN buffer layers. Atomic force microscopy imaging shows that the as-grown and chemically etched Ga-polar films have a flat and pitted surface while the N-polar surface is rougher with isolated columns or islands. Transmission electron microscopy demonstrates a low density of inversion domains in the Ga-polar films,while a much higher density of inversion domains was observed in the N-polar films. X-ray diffractionmore » curves show a narrower (002) peak for Ga-polar films than that for N-polar films. On the other hand, both Ga-and N-polar films show a similar width of (104) peak. Despite their rough surfaces, high density of inversion domains, and broader (002) x-ray diffraction peaks, N-polar films with low dislocation density were demonstrated. In addition, higher PL efficiency for the N-polar films than that for the Ga-polar films was observed.« less
  • The sensitivity of the surface morphology and microstructure of N-polar-oriented InAlN to variations in composition, temperature, and layer thickness for thin films grown by plasma-assisted molecular beam epitaxy (PAMBE) has been investigated. Lateral compositional inhomogeneity is present in N-rich InAlN films grown at low temperature, and phase segregation is exacerbated with increasing InN fraction. A smooth, step-flow surface morphology and elimination of compositional inhomogeneity can be achieved at a growth temperature 50 °C above the onset of In evaporation (650 °C). A GaN/AlN/GaN/200-nm InAlN heterostructure had a sheet charge density of 1.7 × 10{sup 13 }cm{sup −2} and no degradation in mobility (1760 cm{sup 2}/V s)more » relative to 15-nm-thick InAlN layers. Demonstration of thick-barrier high-electron-mobility transistors with good direct-current characteristics shows that device quality, thick InAlN layers can be successfully grown by PAMBE.« less
  • 5-nm thick Co{sub 4}N layers capped with 3-nm thick Au layers were grown epitaxially on SrTiO{sub 3}(001) substrates by molecular beam epitaxy using solid Co and a radio-frequency NH{sub 3} plasma. Spin and orbital magnetic moments of the Co{sub 4}N layers were estimated using x-ray magnetic circular dichroism (XMCD) measurements at 300 K. The site-averaged Co 3d spin magnetic moment is evaluated to be about 1.4 {mu}{sub B}, which is smaller than that predicted theoretically (1.58 {mu}{sub B}). The element-specific XMCD intensities for the Co L{sub 3} edge and N K edge show that the magnetic moment is induced atmore » the N atoms.« less