Etch pit density

The etch pit density (EPD) is a measure for the quality of semiconductor wafers.^[1]^[2]

Etching

An

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. Silicon

wafers have usually a very low density of < 100 cm⁻² while semi-insulating GaAs wafers have a density on the order of 10⁵ cm⁻².

Germanium detectors

High-purity Germanium detectors require the Ge crystals to be grown with a controlled range of dislocation density to reduce impurities. The etch pitch density requirement is typically within the range 10³ to 10⁴ cm⁻².^{[citation needed]}