ISO 5618-1:2023

Overview

ISO 5618-1:2023 - part of the ISO 5618 series on fine/advanced ceramics - defines a standardized classification of surface defects that occur on single-crystal gallium nitride (GaN) substrates and GaN films. This Part 1 document identifies and describes dislocations and process‑induced defects exposed at the GaN surface for:

• single‑crystal GaN substrates;
• homoepitaxial GaN films on GaN substrates;
• heteroepitaxial GaN films on Al2O3 (aluminium oxide), SiC (silicon carbide) or Si (silicon) substrates.

It does not apply when the acute angle between the surface normal and the GaN c‑axis is ≥ 8°.

Key topics and technical requirements

• Defect classification scope: Focused on surface‑exposed dislocations and processing defects relevant to device-quality GaN.
• Dislocation types described with crystallographic context and Burgers vectors:
  • Threading dislocation - extends almost parallel to the c‑axis (includes tilted and helical forms; tilt up to 80°).
  • Threading edge dislocation (TED) - b = n × (|a|/3) <11 2 0>.
  • Threading screw dislocation (TSD) - b = n × |c| <0001> (hollow core variants noted).
  • Threading mixed dislocation (TMD) - b = m × (|a|/3) <11 2 0> + n × |c| <0001>.
  • Basal plane dislocation - located on the basal plane (perpendicular to c‑axis).
• Process‑induced defects:
  • Scratch - linear groove (length:width ≥ 5:1).
  • Latent scratch - groove revealed after chemical etching.
  • Pit - holes or hexagonal truncated‑pyramid/bowl‑shaped features often revealed by etching.
• Terminology: Defines GaN, Burgers vector, c‑axis, etching/etchant, substrate, homo/heteroepitaxy - enabling consistent defect reporting.

Applications and who uses it

ISO 5618-1:2023 is essential for:

• GaN substrate and epitaxial film manufacturers for quality classification and process control.
• LED, LD and power device makers to assess how surface defects affect luminous efficiency, performance and reliability.
• Materials scientists, process engineers and metrology labs performing defect characterization and yield improvement.
• Quality assurance and procurement teams specifying acceptance criteria for GaN wafers and films.

Use cases include setting inspection protocols, benchmarking dislocation types and guiding process improvements to reduce defect densities that degrade device performance.

Related standards

• ISO 5618-2 (under preparation) - Method of determining etch pit density (complements Part 1).
• ISO 15932:2013 - relevant terminology (microbeam analysis).
• IEC 63068-1:2019 - analogous defect classification for SiC wafers.

Keywords: ISO 5618-1:2023, GaN surface defects, gallium nitride, threading dislocation, TED, TSD, TMD, basal plane dislocation, pits, scratches, etch pit density, fine ceramics, advanced ceramics.