Appeal No. 96-3475
Application 08/245,775
trimethylindium is used as indium dopant precursor, the lowest doping achieved is in the mid 1016
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atoms per cm . See the specification at page 2, line 22. This is caused by the relatively high
vapor pressure of trimethylindium. Appellants further indicate that trimethylindium is not a
suitable precursor for doping because it suffers from transport problems. Thus as acknowledged
in the specification at page 2, lines 13-16, since trimethylindium is a solid at or below room
temperature the effective vapor pressure of trimethylindium in a conventional bubbler changes
with time due to changes in the surface area of the solid. In addition, appellants point out that
when trimethylindium is used as the precursor for doping of II/VI semiconductor materials, it has
shown a significant memory effect, i.e., the indium doping persists for a number of growth runs
following the introduction of the trimethylindium source.
Thus, while admitting that indium is the prior art "dopant of choice" which is primarily
provided by trimethylindium as the indium dopant precursor in prior art doping in both
"interdiffusion multilayer and directed alloy growth” processes, appellants indicate that
trimethylindium is the cause of the above mentioned problems when used in such processes. To
solve the problems associated with the use of solid trimethylindium as a dopant precursor,
appellants utilized a liquid indium dopant precursor, i.e., triisopropylindium, which is said to
provide a constant quantity with better control of the dopant at reasonable temperatures, thus
permitting doping at low carrier concentrations with a reduction of the memory effect. Generally
see the specification at page 3.
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