Effects of ultraviolet-assisted electrochemical etching current densities on structural and optical characteristics of porous quaternary AlInGaN alloys

Abstract

Effects of ultraviolet-assisted photo-electrochemical (PEC) etching current densities (J = 20, 40, 80, and 160 mA/cm2) towards structural, physical, and optical properties of aluminium indium gallium nitride (AlInGaN) semiconductors as well as corresponding schematized mechanism were studied and discussed. Formation of porous AlInGaN semiconductors at J lower than 80 mA/cm2 has led to the acquisition of larger lattice parameters c and a, out-of-plane strain, in-plane strain, and hydrostatic strain as compared to the non-porous semiconductor, owing to the generation of more vacancy-type defects in the porous AlInGaN semiconductors. For the porous semiconductor formed at J greater than 80 mA/cm2, the etching was affected by a limited mass transport of electrons and holes for anodic oxidation and cathodic reduction. According to the band gap (Eg) and Urbach energy (UE) determined from photoluminescence (PL) shift and UV–Vis absorption measurement, the vacancy-type defects were revealed as the radiative localized states that led to the enhancement in PL peak intensity. The acquisition of a lower density of dislocation-type defects in the porous semiconductors in contrast to the non-porous one on the other hand indicated that the dislocations were the non-radiative recombination centres, in which much of the density has been eliminated after PEC etching in the 1% potassium hydroxide electrolyte. Keywords: AlInGaN, Porous, Photo-electrochemical, Etching, Optical, Band gap