A method of reusing a III-nitride growth substrate according to embodiments of the invention includes epitaxially growing a III-nitride semiconductor structure on a III-nitride substrate. The III-nitride semiconductor structure includes a sacrificial layer and an additional layer grown over the sacrificial layer. The sacrificial layer is implanted with at least one implant species. The III-nitride substrate is separated from the additional layer at the implanted sacrificial layer. In some embodiments the III-nitride substrate is GaN and the sacrificial layer is GaN, an aluminum-containing III-nitride layer, or an indium-containing III-nitride layer. In some embodiments, the III-nitride substrate is separated from the additional layer by etching the implanted sacrificial layer.