ABSTRACT
Ga0.5In0.5P and GaAs0.5P0.5 layers have been grown on exactly (001) substrates by OMVPE. Only 2 of the 4 possible L11 variants, ( 1 ¯ https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781003069638/440efdcf-c2ed-414a-bdad-7c98e059177f/content/eq233.tif"/> 11) and (1 1 ¯ https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781003069638/440efdcf-c2ed-414a-bdad-7c98e059177f/content/eq234.tif"/> 1), are observed for both materials. To examine the effects of surface steps on ordering, the substrates were first patterned with [110] oriented grooves ~5 μm wide and from 0.2 to 1 μm deep. TEM observations reveal that the two directions of step motion produce two different variants. For GaInP, one half of the groove is filled with a single domain of the ( 1 ¯ https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781003069638/440efdcf-c2ed-414a-bdad-7c98e059177f/content/eq235.tif"/> 11) variant while the other half is a single domain of the (1 1 ¯ https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781003069638/440efdcf-c2ed-414a-bdad-7c98e059177f/content/eq236.tif"/> 1) variant. For GaAsP, single, large ( 1 ¯ https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781003069638/440efdcf-c2ed-414a-bdad-7c98e059177f/content/eq237.tif"/> 11) and (1 1 ¯ https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781003069638/440efdcf-c2ed-414a-bdad-7c98e059177f/content/eq238.tif"/> 1) domains are also produced. However, large, well-defined regions with absolutely no ordering are also observed. These are shown to be due to the growth on {511} facets inadvertently produced at the edges of the grooves during etching. The {511} planes have a higher growth rate, so disappear during growth of the layers, leaving large domains of ordered material. The domains formed in both materials are the largest ever observed, several square microns in cross section and extending along the entire length of the groove.
