Strain relaxation in GaN/Al{sub x}Ga{sub 1-x}N superlattices grown by plasma-assisted molecular-beam epitaxy

Journal Article · Mon Aug 01 00:00:00 EDT 2011 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.3618680· OSTI ID:22036674

Kotsar, Y; Bellet-Amalric, E; Das, A; Monroy, E ^[1]; Doisneau, B ^[2]; Sarigiannidou, E ^[3]

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1. CEA-Grenoble, INAC/SP2M/NPSC, 17 Rue des Martyrs, 38054 Grenoble cedex 9 (France)
2. SIMaP, Grenoble INP, Domaine Universitaire, BP 75, 38402 Saint Martin d'Heres (France)
3. LMGP, Grenoble INP, 3 Parvis Louis Neel, BP 257, 38016 Grenoble cedex 1 (France)

We have investigated the misfit relaxation process in GaN/Al{sub x}Ga{sub 1-x}N (x = 0.1, 0.3, 0.44) superlattices (SL) deposited by plasma-assisted molecular beam epitaxy. The SLs under consideration were designed to achieve intersubband absorption in the mid-infrared spectral range. We have considered the case of growth on GaN (tensile stress) and on AlGaN (compressive stress) buffer layers, both deposited on GaN-on-sapphire templates. Using GaN buffer layers, the SL remains almost pseudomorphic for x = 0.1, 0.3, with edge-type threading dislocation densities below 9 x 10{sup 8} cm{sup -2} to 2 x 10{sup 9} cm{sup -2}. Increasing the Al mole fraction to 0.44, we observe an enhancement of misfit relaxation resulting in dislocation densities above 10{sup 10} cm{sup -2}. In the case of growth on AlGaN, strain relaxation is systematically stronger, with the corresponding increase in the dislocation density. In addition to the average relaxation trend of the SL, in situ measurements indicate a periodic fluctuation of the in-plane lattice parameter, which is explained by the different elastic response of the GaN and AlGaN surfaces to the Ga excess at the growth front. The results are compared with GaN/AlN SLs designed for near-infrared intersubband absorption.

• OSTI ID: 22036674
• Journal Information: Journal of Applied Physics, Vol. 110, Issue 3; Other Information: (c) 2011 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ABSORPTION
ALUMINIUM NITRIDES
CRYSTAL GROWTH
DISLOCATIONS
ELASTICITY
FLUCTUATIONS
GALLIUM NITRIDES
INFRARED SPECTRA
LATTICE PARAMETERS
LAYERS
MOLECULAR BEAM EPITAXY
PLASMA
RELAXATION
SAPPHIRE
SEMICONDUCTOR MATERIALS
STRAINS
STRESSES
SUPERLATTICES