The nature and origin of lateral composition modulations in short-period strained-layer superlattices

Conference · Mon Feb 28 00:00:00 EST 2000

DOI:https://doi.org/10.1557/PROC-583-297· OSTI ID:754732

Norman, A G; Ahrenkiel, S P; Moutinho, H R; Ballif, C; Al-Jassim, M M; Mascarenhas, A; Follstaedt, D M; Lee, S R; Reno, J L; Jones, E D; Mirecki-Millunchick, J; Twesten, R D

The nature and origin of lateral composition modulations in (AlAs){sub m}(InAs){sub n} short-period strained-layer superlattices (SPS) grown by molecular-beam epitaxy on InP substrates have been investigated by X-ray diffraction, atomic force microscopy, and transmission electron microscopy. Strong modulations were observed for growth temperatures between approximately 540 and 560 C. The maximum strength of modulations was found for SPS samples with InAs mole fraction x (= n/(n+m)) close to approximately 0.50 and when n is approximately equal to m approximately equal to 2. The modulations were suppressed at both high and low values of x. For x > 0.52 (global compression), the modulations were along the <100> directions in the (001) growth plane. For x < 0.52 (global tension), the modulations were along the two <310> directions rotated approximately {+-}27{degree} from [110] in the growth plane. The remarkably constant wavelength of the modulations, between approximately 20--30 nm, and the different modulation directions observed suggest that the origin of the modulations is due to surface roughening associated with the high misfit between the individual SPS layers and the InP substrate. Highly uniform unidirectional modulations have been grown by control of the InAs mole fraction and growth on suitably offcut substrates, which show great promise for application in device structures.

• Research Organization: National Renewable Energy Lab. (NREL), Golden, CO (United States)
• Sponsoring Organization: US Department of Energy (US)
• DOE Contract Number: AC36-99GO10337
• OSTI ID: 754732
• Report Number(s): NREL/CP-520-27811; TRN: AH200013%%48
• Resource Relation: Journal Volume: 583; Conference: Materials Research Society's Fall 1999 Meeting, Boston, MA (US), 11/29/1999--12/03/1999; Other Information: PBD: 28 Feb 2000
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
14 SOLAR ENERGY
CHEMICAL COMPOSITION
MICROSTRUCTURE
ALUMINIUM ARSENIDES
INDIUM ARSENIDES
SUPERLATTICES
INDIUM PHOSPHIDES
SUBSTRATES
MOLECULAR BEAM EPITAXY
SOLAR CELLS
PHOTOVOLTAICS
LATERAL COMPOSITION MODULATIONS
MOLECULAR-BEAM EPITAXY
X-RAY DIFFRACTION
ATOMIC FORCE MICROSCOPY
TRANSMISSION ELECTRON MICROSCOPY