Patent ID: 8858709

Claim:
A physical vapor deposition method of growing a crystal comprising: (a) providing a source crucible charged with source material inside of an enclosed growth crucible which at least in-part has a first permeability to an unwanted gas that is present in the charged growth crucible, wherein said part of the growth crucible has a second, lower permeability to sublimated source material; (b) providing a seed crystal in the growth crucible in spaced relation to the source crucible; (c) heating the interior of the growth crucible whereupon the source material is at a first temperature sufficient to sublimate the source material and the seed crystal is at a second, lower temperature sufficient to cause the sublimated source material to be transported to the seed crystal where the sublimated source material precipitates; and (d) concurrent with step (c), causing a purging gas to flow either inside or outside of the growth crucible, which is also permeable to the purging gas, at a flow rate whereupon a concentration gradient of the unwanted gas forms across said part of the growth crucible, whereupon the unwanted gas flows from the inside to the outside of the growth crucible via said part of the growth crucible.