Standards Development

Scope

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

It is applicable to the defects specified in AWI 5618-1 from among the defects cropped out 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 or lower.

Purpose

GaN is a direct transition type of wide-bandgap semiconductor with superior physical properties, such as a higher breakdown electric field, saturated electron drift velocity, and thermal conductivity, than those of Si. GaN is expected to be applied not only in light-emitting devices that have been in practical use for a long time, such as ultraviolet and blue LDs and LEDs, but also in power devices that perform power conversion with high efficiency. In particular, the characteristics of GaN power devices are utilised in the fields of photovoltaics, automobiles, railways (electric motors and linear motors), communication base stations, and microwave power transmission.

The single-crystal GaN or single-crystal GaN film is the base material of devices. However, the surface of the single-crystal GaN or single-crystal GaN film contains many dislocations that are introduced during the crystal growth and defects that are introduced during wafer processing. These dislocations and/or defects cause a decrease in luminous efficiency for a light-emitting device and a decrease in performance and reliability for a power device. In particular, given the practical applications and market expansion of power devices that apply a high voltage and high current, it is indispensable to supply single-crystal GaN substrates and single-crystal GaN films with a low-density of dislocations and defects. Therefore, it is essential to have an international standard that defines and classifies the types of dislocations and processing-introduced defects that exist on the surface as an index for assessing the quality of a single-crystal GaN substrate or a single-crystal GaN film and determines the density of these dislocations and defects.

The series consist of Part 1 and Part 2, as described below. Part 2 describes the detection, counting, and classification of the dislocations and processing-introduced defects cropped out on the surface of single-crystal GaN substrates and single-crystal GaN films based on etching. These single-crystal substrates and films are mainly used for light-emitting devices, such as LDs and LEDs and power devices that perform high-voltage and high-current power conversion.

Part 1: Classification of defects

Part 2: Method of determining the etch pit density