Step structure during organometallic vapor phase epitaxial growth of ordered GaInP

Abstract

The nature of the steps on the nominally (00l)-oriented surface of Ga0.5In0.5P lattice matched to GaAs has been studied using high resolution atomic force microscopy. The layers were grown by organometallic vapor phase epitaxy (OMVPE) at a temperature of 620°C on substrates misoriented by angles,ϑm, from 0 to 9° toward the % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfKttLearuqr1ngBPrgarmqr1ngBPrgitL% xBI9gBamXvP5wqSXMqHnxAJn0BKvguHDwzZbqegm0B1jxALjhiov2D% aeHbuLwBLnhiov2DGi1BTfMBaebbfv3ySLgzGueE0jxyaibaieYlf9% irVeeu0dXdh9vqqj-hEeeu0xXdbba9frpe0db9Lqpepeea0xd9q8as% 0-LqLs-Jirpepeea0-as0Fb9pgea0lrP0xe9Fve9Fve9qapdbaqaae% GaciGaaiaabeqaamaaeaqbaaGcbaGaei4waSLafGymaeJbaebacqaI% XaqmcqaIWaamcqGGDbqxaaa!482D! $$[\bar 110]$$ direction in the lattice. An array of bunched steps from 25 to 50A in height, depending on the substrate misorientation angle, is observed on the surface. An unusual feature of these bunched or super-steps, as compared to those seen for GaAs surfaces, is that they have relatively short lengths of a few thousand Angstroms. In addition, not all of the steps congregate into the surface steps. Thus, the surface consists of three “phases”: (001) flats, (11n) facets, and misoriented areas covered by an array of monolayer steps. The fraction of steps contained in the supersteps decreases monotonically as ϑm increases from 3 to 9°. Again, this differs from reports of the nature of GaAs surfaces grown under similar conditions where essentially all of the steps congregate into supersteps. The value of n for the (lln) facets also varies with misorientation angle: The angle between the (001) and the (lln) facets increases from approximately 11-12° for ϑm = 3° to nearly 30† for ϑm = 9°. An attempt was made to correlate the surface structure with ordering, which is observed to vary significantly with misorientation angle. The degree of order is found to increase monotonically with the fraction of steps forming supersteps.