EFFECTS OF GAAS-SUBSTRATE SURFACE MISORIENTATION FROM (001) ON BAND-GAP ENERGY IN GA0.5IN0.5P

The dependence of band-gap energy (E(g)) on GaAs-substrate surface orientation was systematically studied for metalorganic vapor phase epitaxial growth Ga0.5In0.5P on GaAs at a growth temperature of 660-degrees-C and a V/III ratio of 140 approximately 150. When the misorientation angle theta(B) increased from the exact (001) to (111)B, E(g) decreased from 1.85 eV and took a minimum value of 1.83 eV at theta(B) = 4-degrees approximately 6-degrees. When theta(B) increased from 4-degrees approximately 6-degrees to 15.8-degrees (i.e., (115)B), E(g) increased steeply to a nearly-normal value of 1.90 eV. Then, E(g) gradually reached a normal value of 1.918 eV, as theta(B) reached 54.7-degrees (i.e., (111)B). The (115)B surface was found to be a critical misorientation. On the other hand, when increasing the misorientation angle theta(A) from the exact (001) to (111)A by 4-degrees approximately 6-degrees, E(g) increased sharply towards the normal value. For further increase of theta(A), E(g) still increased monotonically towards a value of 1.916 eV at (111)A, which is virtually the same as that for the (111)B surface. These E(g) behaviors were found to correspond to the degree of ordering characterized by the transmission electron microscopic study of (111)B CuPt-type ordering on the Group III sublattice. A possible explanation is given for the E(g) behaviors on the basis of step-terrace reconstructions on the grown surfaces.