EFFECTS OF SUBSTRATE MISORIENTATION AND GROWTH-RATE ON ORDERING IN GAINP

Epitaxial layers of GaxIn1-xP with x almost-equal-to 0.52 have been grown by_organometallic vapor-phase epitaxy on GaAs substrates misoriented from the (001) plane in the [110] direction by angles theta(m), of 0-degrees, 3-degrees, 6-degrees, and 9-degrees. For each substrate orientation growth rates r(g) of 1, 2, and 4 mum/h have been used. The ordering was characterized using transmission electron diffraction (TED), dark-field imaging, and photoluminescence. The (110) cross-sectional images show domains of the Cu-Pt structure separated by antiphase boundaries (APBs). The domain size and shape and the degree of order are found to be strongly affected by both the substrate misorientation and the growth rate. For example, lateral domain dimensions range from 50 angstrom for layers grown with r(g) = 4 mum/h and theta(m) = 0-degrees to 2500 angstrom for r(g) = 1 mum/h and theta(m) = 9-degrees. The APBs generally propagate from the substrate/epilayer interface to the top surface at an angle to the (001) plane that increases dramatically as the angle of misorientation increases. The angle is nearly independent of growth rate. From the superspot intensities in the TED patterns, the degree of order appears to be a maximum for theta(m) almost-equal-to 5-degrees. Judging from the reduction in photoluminescence peak energy caused by ordering, the maximum degree of order appears to occur at theta(m) almost-equal-to 4-degrees.