Patent ID: 8357243

Claim:
A method of testing a first set of group III-nitride substrates cut from an ingot formed using a seed material, said method comprising a) selecting substrates from the first set of substrates to form a second set of substrates, the second set of substrates being a subset of the first set and therefore being a selection of substrates from the first set of substrates that does not include all members from the first set of substrates, b) analyzing samples taken from the substrates of the second set to assess values of a first property of each of the substrates of the second set, c) determining a correlation for the values of the first property, said correlation being a function of distance of each of said substrates of the second set from a seed used to form the ingot, and d) applying said correlation to substrates not in said second set of substrates to provide estimated values of said first property for said substrates, wherein e) the ingot was produced using an ammonothermal process, wherein f) the testing is carried out on at least one of the crystallographic planes selected from Group III-polar side c plane, nitride-polar side c plane, m plane, or {101} plane, and wherein g) the substrate is cut at an angle to the crystallographic plane.