Relaxed In_xGa_1-xAs graded buffers grown with organometallic vapor phase epitaxy on GaAs

In_xGa_1-xAs structures with compositionally graded buffers were grown with organometallic vapor phase epitaxy on GaAs substrates and characterized with plan-view and cross-sectional transmission electron microscopy, atomic force microscopy, and x-ray diffraction. The results show that surface roughness experiences a maximum at growth temperatures where phase separation occurs in In_xGa_1-xAs. The strain fields from misfit dislocations induce this phase separation in the <110> directions. At growth temperatures above and below this temperature, the surface roughness is decreased significantly; however, only growth temperatures above this regime ensure nearly complete relaxed graded buffers with the most uniform composition caps. With the optimum growth temperature for grading In_xGa_1-xAs determined to be 700 °C, it was possible to produce In_0.33Ga_0.67As diode structures on GaAs with threading dislocation densities ≪8.5×10⁶/cm². © 1998 American Institute of Physics.