Anodic Etching of n-GaN Epilayer into Porous GaN and Its Photoelectrochemical Properties

Porous n-GaN has been fabricated using electrochemical anodic etching in a 0.5 M H2SO4 solution in the dark for different biases (5.5-18.0 V). The pore morphology of the porous GaN shows distinctive differences: from narrow branching pores to wide parallel pores for increasing applied bias. The pore formation process has been investigated using cyclic voltammetry and chronoamperometry. The photoelectrochemical properties of these porous n-GaN layers have been examined. For the porous GaN etched at 5.5-15.0 V, the plateau photocurrent increases over 4 times, and the potential difference between the current onset and the plateau is reduced by 0.24 V with respect to unetched, planar n-GaN.