Hyperbolic-tangent composition-graded InxGa1-xAs/GaAs (100) structures grown by molecular beam epitaxy

The molecular beam epitaxial growth and physical properties of In graded-composition layers of InGaAs on GaAs (100) substrates varying nominal In concentration from 12 to 97% and vice versa is analyzed along the growth front. The substrate temperature was varied as the In concentration was changed in order to propitiate the near optimal growth conditions for the InGaAs alloy. Hyperbolic-tangent compositional gradients, from In-rich to Garich alloys and vice versa, observed RHEED patterns characteristic of a flat surface during the growth. The HRXRD patterns showed clear diffraction peaks associated with the In concentration alloy at which the graded sample started, followed by a characteristic plateau of graded layers. The occurrence of dislocations in hyperbolic tangent gradients that relieve the strain up to a certain thickness is explored, reaching a nominal or an averaged lattice constant.