Appeal No. 1998-1665 Page 3
Application No. 08/476,831
OPINION
Claim 1 is directed to an optical window consisting essentially of a group III-V compound that
has been doped with a dopant in a concentration of from about 5 x 10 to about15
2 x 10 atoms/cc. The dopant is an element taken from the class consisting of shallow donors. The16
specification indicates that selenium (Se) is a preferred shallow donor dopant (specification, page 6).
Claim 1 also limits the level of carbon impurity to less than about 1 x 10 atoms/cc. The material of the7
optical window is formed by crystallizing a melt of the doped group III-V compound in a carbon cloth
covered graphite crucible subjected to a vertical temperature gradient (specification, pages 8-9).
According to the specification, if the carbon level in the melt is greater than 1 x 10 atoms/cc, then an7
increased amount of Se dopant must be used, such as about 5 x 10 atoms/cc (specification, page 6).16
The specification indicates that increasing the Se doping level results in a lowering of the mobility of the
electrons and increased non-uniformity and provides an inferior result (specification, page 8).
Therefore, a boron oxide with a water content of 450-550 ppm is added to the melt to assist in removal
of impurities, particularly carbon (Id.).
The examiner rejects the claims over McNeely in view of Bult. McNeely describes a process
of forming GaAs semiconductor single crystals including GaAs double-doped with oxygen and
selenium. McNeely is silent as to the level of carbon. Bult is added to the rejection for the teaching of
using wet boron oxide encapsulant in the growing of a GaAs semiconductor single crystal. The
examiner concludes from the teachings of McNeely and Bult that one ordinary skill in the art would
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