Separation of laterally overgrown GaN template by using selective electrochemical etching

Abstract

Selective lateral electrochemical etching was employed for detaching a GaN layer with lowered dislocation density produced by maskless epitaxial lateral overgrowth (ELO) process. The dislocation density in the ELO regions was more than an order of magnitude lower than in the reference regions. The separation of the ELO GaN template from sapphire substrate was achieved by selective lateral electrochemical etching in an oxalic acid. It was shown that such etching occurred preferentially along the GaN template/ELO interface by first creating small pores at the interface and then enlarging them. The etching rates as high as 150μm/min could be achieved, resulting in complete detachment of the entire ELO GaN film. The detached GaN films were transferred to glass substrates and bonded with conducting epoxy. Photoluminescence measurements showed a high luminescence efficiency and decreased strain in the detached ELO GaN template.