Energy Band/Lattice Mismatch Engineering in Quaternary AlInGaN/GaN Heterostructure

We discuss structural, optical and electrical properties of AlxInyGa1—x—yN/GaN heterostructures grown on sapphire and 6H-SiC substrates. The incorporation of In reduces the lattice mismatch in a much stronger way than the energy gap discontinuity. An In to Al ratio close to 1:5 should result in nearly strain-free heterostructures. The incorporation of In and resulting changes in the built-in strain in AlInGaN/GaN heterostructures strongly affect the transport properties of the two-dimensional (2D) electron gas at the heterointerface. Using the incorporation of In in order to increase the Al molar fraction preserving the same value of strain should allow us to greatly enhance the sheet carrier density at the AlGaInN/GaN heterointerface. Further work on improving In incorporation techniques is needed in order to meet these expectations.