(Al,In)N layers and (Al,In)N/GaN heterostructures grown by plasma-assisted molecular beam epitaxy on 6H-SiC(0001)

Journal Article · Tue Jul 15 00:00:00 EDT 2008 · Physical Review. B, Condensed Matter and Materials Physics

DOI:https://doi.org/10.1103/PHYSREVB.78.035311· OSTI ID:21143597

Ive, Tommy; Brandt, Oliver; Xiang, Kong; Trampert, Achim; Ploog, Klaus H ^[1]

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1. Paul-Drude-Institut fuer Festkoerperelektronik, Hausvogteiplatz 5-7, D-10117 Berlin (Germany)

We study the properties of (Al,In)N layers and (Al,In)N/GaN heterostructures grown on 6H-SiC(0001) by plasma-assisted molecular beam epitaxy. The (Al,In)N films are deposited on a GaN buffer layer. A growth temperature of 500 deg. C and above results in low In contents which give rise to cracks due to the large tensile strain experienced from the underlying GaN buffer layer. In addition, these layers exhibit strong phase separation leading to inhomogeneous In composition and rough surfaces. In contrast, samples with homogeneous and well-controlled In-contents between 10%-30% are reproducibly obtained in the temperature range of 250-350 deg. C. Surprisingly, nominally lattice-matched layers with an In content of 17%-18% also exhibit cracks. Symmetric {omega}-2{theta} x-ray diffraction scans and reciprocal space maps reveal the presence of a strain gradient in these layers despite the apparently lattice-matched conditions. Transmission electron microscopy indicates that these cracks are the result of tensile stresses induced by crystallite coalescence and grain-boundary formation. This mechanism can be counteracted by augmenting the adatom mobility through increasing the growth temperature and the N flux. However, phase separation sets an upper limit on the growth temperature and a moderate increase to 350-400 deg. C is sufficient to obtain crack-free and homogeneous (Al,In)N layers. The results of our growth experiments lead to a phase diagram which shows the optimum growth window for (Al,In)N layers. By choosing the growth conditions within this window, we are able to obtain crack-free Al{sub 0.82}In{sub 0.18}N/GaN multilayers with abrupt interfaces.

• OSTI ID: 21143597
• Journal Information: Physical Review. B, Condensed Matter and Materials Physics, Vol. 78, Issue 3; Other Information: DOI: 10.1103/PhysRevB.78.035311; (c) 2008 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 1098-0121
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM COMPOUNDS
CRYSTAL GROWTH
FILMS
GALLIUM NITRIDES
GRAIN BOUNDARIES
INDIUM COMPOUNDS
INTERFACES
LAYERS
MOBILITY
MOLECULAR BEAM EPITAXY
PHASE DIAGRAMS
RESIDUAL STRESSES
SEMICONDUCTOR MATERIALS
SILICON CARBIDES
STRAINS
SUBSTRATES
SURFACES
TEMPERATURE RANGE 0400-1000 K
TRANSMISSION ELECTRON MICROSCOPY
X-RAY DIFFRACTION