INFLUENCES OF SUBSTRATE SURFACE ORIENTATION ON MISFIT ACCOMMODATION IN INGAP GAAS HETEROSTRUCTURES/

The effect of crystallographic tilt of the substrate on the misfit str ain and stress are investigated in this study. InGaP/GaAs heterostruct ure wafers are grown on two types of substrates with normal [100] orie ntation and 7 degrees (+/- 0.2 degrees) tilted from [100] toward [110] orientation. Lattice mismatches are measured using 511 asymmetric and 400 symmetric reflections. The lattice misfits and the elastic strain s are also measured. The elastic strain-lattice misfit relation shows that larger strain is developed in the layers grown on the tilted subs trate. The radius of curvature, R, plotted as a function of lattice mi sfit reveals that larger R, in general, is obtained from the sample wi th smaller misfit. It also shows that R is smaller in the tilted sampl e even when the lattice misfit is identical to that of the normal samp le. It is also found that the misfit stress is larger in the tilted sa mple. The results presented show that the characteristics of misfit ac commodation are improved in the layers grown on the tilted substrate.