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 gr own by_organometallic vapor-phase epitaxy on GaAs substrates misorient ed 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 ori entation growth rates r(g) of 1, 2, and 4 mum/h have been used. The or dering 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 bou ndaries (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-degree s to 2500 angstrom for r(g) = 1 mum/h and theta(m) = 9-degrees. The AP Bs generally propagate from the substrate/epilayer interface to the to p surface at an angle to the (001) plane that increases dramatically a s the angle of misorientation increases. The angle is nearly independe nt 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 en ergy caused by ordering, the maximum degree of order appears to occur at theta(m) almost-equal-to 4-degrees.