The Investigation of Porous AlxGa1-xN Layers on Si (111) Substrate with GaN/AlN as Buffer Layer

High quality undoped AlxGa1-xN with high Ga composition was grown on Si (1 1 1) substrate, using GaN/AlN as the buffer layer, by plasma-assisted molecular beam epitaxy (PAMBE). The present work reports on the photoluminescence (PL) studies of porous AlxGa1-xN prepared by ultraviolet (UV) assisted electrochemical etching in a solution of 2 % concentration of KOH electrolyte under illumination of an UV lamp with 500 W power for 30 min. The optical properties of porous AlxGa1-xN sample was compared to the corresponding as-grown GaN. PL studies suggested that the porosity was capable of improving the lattice mismatch induced strain. Porosity induced PL intensity enhancement was found in nanoporous sample. The resulting nanoporous AlxGa1-xN display red-shifted PL spectra compared to the as-grown AlxGa1-xN. Appearance of the red-shifted emission is correlated with the development of highly anisotropic structures in the morphology.