ISO 21820:2021 specifies a test method for determining the polytypes and their ratios in silicon carbide (SiC) wafers or bulk crystals using ultraviolet photoluminescence (UVPL) imaging. The range of SiC is limited to semiconductor SiC doped with nitrogen and boron to have a deep acceptor level and a shallow donor level, respectively. The SiC wafers or bulk crystals discussed in this document typically show electrical resistivities ranging from 10 ohm · cm to 10 ohm · cm, applicable to power electronic devices.
This method is applicable to the SiC-crystal 4H, 6H and 15R polytypes that contain boron and nitrogen as acceptor and donor, respectively, at concentrations that produce donor-acceptor pairs (DAPs) to generate UVPL. In 4H-SiC the boron and nitrogen concentrations typically range from 10 cm to 10 cm . Semi-insulating SiC is not of concern because it usually contains minimal boron and nitrogen; therefore deep level cannot be achieved.
