skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Fine structure of AlN/AlGaN superlattice grown by pulsed atomic-layer epitaxy for dislocation filtering

Abstract

We report the detailed structure analysis of our AlN/AlGaN superlattice (SL) grown by pulsed atomic-layer epitaxy (PALE) for dislocation filtering. Due to the nature of PALE, the AlGaN well material itself in the SL was found to be composed actually of an Al{sub x}Ga{sub 1-x}N/Al{sub y}Ga{sub 1-y}N short-period superlattice (SPSL), with the periodicity of 15.5 A ({approx_equal}6 monolayer), determined consistently from high-resolution x-ray diffraction and high-resolution transmission electron microscopy measurements. The SPSL nature of the AlGaN layers is believed to benefit from the AlN/AlGaN SL's coherent growth, which is important in exerting compressive strain for the thick upper n-AlGaN film, which serves to eliminate cracks. Direct evidence is presented which indicates that this SL can dramatically reduce the screw-type threading dislocation density.

Authors:
; ; ; ; ; ;  [1];  [2]
  1. Department of Electrical Engineering, University of South Carolina, Columbia, South Carolina 29208 (United States)
  2. (United States)
Publication Date:
OSTI Identifier:
20706431
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 87; Journal Issue: 21; Other Information: DOI: 10.1063/1.2136424; (c) 2005 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ALUMINIUM NITRIDES; CRACKS; CRYSTAL GROWTH; DISLOCATIONS; EPITAXY; FILMS; FINE STRUCTURE; GALLIUM NITRIDES; LAYERS; PERIODICITY; RESOLUTION; SEMICONDUCTOR MATERIALS; SUPERLATTICES; TRANSMISSION ELECTRON MICROSCOPY; X-RAY DIFFRACTION

Citation Formats

Sun, W.H., Zhang, J.P., Yang, J.W., Maruska, H.P., Khan, M. Asif, Liu, R., Ponce, F.A., and Department of Physics and Astronomy, Arizona State University, Tempe, Arizona 85287. Fine structure of AlN/AlGaN superlattice grown by pulsed atomic-layer epitaxy for dislocation filtering. United States: N. p., 2005. Web. doi:10.1063/1.2136424.
Sun, W.H., Zhang, J.P., Yang, J.W., Maruska, H.P., Khan, M. Asif, Liu, R., Ponce, F.A., & Department of Physics and Astronomy, Arizona State University, Tempe, Arizona 85287. Fine structure of AlN/AlGaN superlattice grown by pulsed atomic-layer epitaxy for dislocation filtering. United States. doi:10.1063/1.2136424.
Sun, W.H., Zhang, J.P., Yang, J.W., Maruska, H.P., Khan, M. Asif, Liu, R., Ponce, F.A., and Department of Physics and Astronomy, Arizona State University, Tempe, Arizona 85287. Mon . "Fine structure of AlN/AlGaN superlattice grown by pulsed atomic-layer epitaxy for dislocation filtering". United States. doi:10.1063/1.2136424.
@article{osti_20706431,
title = {Fine structure of AlN/AlGaN superlattice grown by pulsed atomic-layer epitaxy for dislocation filtering},
author = {Sun, W.H. and Zhang, J.P. and Yang, J.W. and Maruska, H.P. and Khan, M. Asif and Liu, R. and Ponce, F.A. and Department of Physics and Astronomy, Arizona State University, Tempe, Arizona 85287},
abstractNote = {We report the detailed structure analysis of our AlN/AlGaN superlattice (SL) grown by pulsed atomic-layer epitaxy (PALE) for dislocation filtering. Due to the nature of PALE, the AlGaN well material itself in the SL was found to be composed actually of an Al{sub x}Ga{sub 1-x}N/Al{sub y}Ga{sub 1-y}N short-period superlattice (SPSL), with the periodicity of 15.5 A ({approx_equal}6 monolayer), determined consistently from high-resolution x-ray diffraction and high-resolution transmission electron microscopy measurements. The SPSL nature of the AlGaN layers is believed to benefit from the AlN/AlGaN SL's coherent growth, which is important in exerting compressive strain for the thick upper n-AlGaN film, which serves to eliminate cracks. Direct evidence is presented which indicates that this SL can dramatically reduce the screw-type threading dislocation density.},
doi = {10.1063/1.2136424},
journal = {Applied Physics Letters},
number = 21,
volume = 87,
place = {United States},
year = {Mon Nov 21 00:00:00 EST 2005},
month = {Mon Nov 21 00:00:00 EST 2005}
}
  • The behavior of dislocations in a GaN layer grown on a 4-inch Si(111) substrate with an AlGaN/AlN strained layer superlattice using horizontal metal-organic chemical vapor deposition was observed by transmission electron microscopy. Cross-sectional observation indicated that a drastic decrease in the dislocation density occurred in the GaN layer. The reaction of a dislocation (b=1/3[-211-3]) and anothor dislocation (b =1/3[-2113]) to form one dislocation (b =2/3[-2110]) in the GaN layer was clarified by plan-view observation using weak-beam dark-field and large-angle convergent-beam diffraction methods.
  • AlGaN/AlN/GaN heterostructures were grown on 6H-SiC, GaN-on-sapphire, and free-standing GaN, resulting in heterostructures with threading dislocation densities of {approx}2 Multiplication-Sign 10{sup 10}, {approx}5 Multiplication-Sign 10{sup 8}, and {approx}5 Multiplication-Sign 10{sup 7} cm{sup -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 {approx}2 nm AlN interlayer and a threading dislocation density of {approx}5 Multiplication-Sign 10{sup 7} cm{sup -2} achieved the very low room temperature sheetmore » resistance of 175 {Omega}/{open_square}.« less
  • A method of reducing threading dislocation (TD) density in AlN epilayers grown on sapphire substrate is reported. By introducing an AlN buffer layer grown by a pulsed atomic-layer epitaxy method, TDs in epitaxial AlN films were greatly decreased. From transmission electron microscopic images, a clear subinterface was observed between the buffer layer and the subsequently continuous grown AlN epilayer. In the vicinity of the subinterface, the redirection, annihilation, and termination of TDs were observed. The increase in lateral growth rate accounted for TD redirection and annihilation in the AlN epilayer. Strain variation between the two regions resulted in the terminationmore » of TDs owing to the dislocation line energy minimization.« less
  • Abstract not provided.
  • We present a far-infrared transmission study on group-III nitride thin films. Cubic GaN and AlN layers and c-oriented wurtzite GaN, AlN, and Al{sub x}Ga{sub 1-x}N (x<0.3) layers were grown by molecular beam epitaxy on GaAs and Si(111) substrates, respectively. The Berreman effect allows us to observe simultaneously the transverse optic and the longitudinal optic phonons of both the cubic and the hexagonal films as transmission minima in the infrared spectra acquired with obliquely incident radiation. We discuss our results in terms of the relevant electromagnetic theory of infrared transmission in cubic and wurtzite thin films. We compare the infrared resultsmore » with visible Raman-scattering measurements. In the case of films with low scattering volumes and/or low Raman efficiencies and also when the Raman signal of the substrate material obscures the weaker peaks from the nitride films, we find that the Berreman technique is particularly useful to complement Raman spectroscopy.« less