High-quality In_xGa_(1-x)As heterostructures grown on GaAs with MOVPE

摘要

In_xGa_(1-x)As structures with compositionally graded buffers were grown by metal-organic vapor phase epitaxy (MOVPE) on GaAs substrates and characterized with plan-view and cross-sectional transmission electron microscopy (PV-TEM and X-TEM), atomic force microscopy (AFM), and x-ray diffraction (XRD). The results show that surface roughness experiences a maximum at growth temperatures where phase separation occurs in In_xGa_(1-x)As. The strain energy due misfit dislocations oin the graded buffer indirectly influences phase separation. 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-x) As determined to be 700 deg, it was possible to produce In_(0.33)Ga_(0.67)As diode structures on GaAs with threading dislocation densities <8.5x10~6/cm~2.