This document describes a method for determining the etch pit density, which is used to detect dislocations and processing-introduced defects that occur on single-crystal GaN substrates or single-crystal GaN films.

It is applicable to the defects specified in ISO 5618‑1 from among the defects exposed on the surface of the following types of GaN substrates or films: single-crystal GaN substrate; single-crystal GaN film formed by homoepitaxial growth on a single-crystal GaN substrate; or single-crystal GaN film formed by heteroepitaxial growth on a single-crystal Al₂O₃, SiC, or Si substrate.

It is applicable to defects with an etch pit density of ≤ 7 × 10⁷ cm^-2.