The etch pit density (EPD) is a measure for the quality of semiconductor wafers.
For GaAs one uses typically molten KOH at 450 degrees Celsius for about 40 minutes in a zirconium crucible.
The density of the pits can be determined by optical contrast microscopy.
High-purity Germanium detectors require the Ge crystals to be grown with a controlled range of dislocation density to reduce impurities.
[citation needed] The etch pit density can be determined according to DIN 50454-1 and ASTM F 1404.