Atomic ordering in GaAsP

Journal Article · Mon Apr 15 04:00:00 EDT 1991 · Journal of Applied Physics; (USA)

DOI:https://doi.org/10.1063/1.348398· OSTI ID:5620390

Chen, G S; Jaw, D H; Stringfellow, G B ^[1]

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1. Department of Materials Science and Engineering and Electrical Engineering, 304 EMRO, University of Utah, Salt Lake City, Utah 84112 (US)

CuPt type ordering, which consists of a monolayer compositional modulation along one of the 4 {l angle}111{r angle} directions in the lattice, was studied using transmission electron microscopy for GaAs{sub 1{minus}{ital x}}P{sub {ital x}} with values of {ital x} extending from 0.25 to 0.85. The samples were grown by organometallic vapor phase epitaxy on nominal (001) GaAs substrates that were misoriented by varying amounts in three directions. No CuPt type ordering was observed for GaAs{sub 1{minus}{ital x}}P{sub {ital x}} with {ital x} {le}0.35, while ordering was found to occur for 0.4{le}{ital x}{le}0.85. The direction of substrate misorientation has a major effect on the determination of which of the four possible CuPt variants are formed for 0.4{le}{ital x}{le}0.85. Two variants, with ordering on the ({bar 1}11) and (1{bar 1}1) planes, appear for epilayers grown on substrates oriented exactly on the (001) plane and for substrates misoriented by 6{degree} towards the (110) direction. Only one variant, with ordering on the ({bar 1}11) plane, appears for epilayers grown on substrates misoriented by 6{degree} towards ({bar 1}10). These ordering-induced spots observed in transmission electron diffraction (TED) patterns for GaAsP occur only for the (110) cross section. From TED studies of GaInP grown on similar substrates, we conclude that the CuPt variants in GaAsP are exactly the same as for GaInP. Further evidence supporting this conclusion was obtained by growing first a layer of GaInP followed by a layer of GaAsP. High-resolution dark field electron micrographs show domains of the same variants in both layers. A mechanism describing the formation of the specific ordered variant for both GaAsP and GaInP is proposed. From studies of ordering in a strain-layer superlattice, the strain due to lattice mismatch was found to play no significant role in the propagation of ordered domains.

• DOE Contract Number: FG02-84ER45061
• OSTI ID: 5620390
• Journal Information: Journal of Applied Physics; (USA), Journal Name: Journal of Applied Physics; (USA) Vol. 69:8; ISSN 0021-8979; ISSN JAPIA
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360602* -- Other Materials-- Structure & Phase Studies
ARSENIC COMPOUNDS
ARSENIDES
CRYSTAL STRUCTURE
CRYSTAL-PHASE TRANSFORMATIONS
DOMAIN STRUCTURE
ELECTRON MICROSCOPY
EPITAXY
GALLIUM ARSENIDES
GALLIUM COMPOUNDS
GALLIUM PHOSPHIDES
LAYERS
MICROSCOPY
PHASE TRANSFORMATIONS
PHOSPHIDES
PHOSPHORUS COMPOUNDS
PNICTIDES
STRAINS
STRUCTURAL MODELS
TRANSMISSION ELECTRON MICROSCOPY