Heterojunction Diode Manufactured With SRC Light
Peter Dowben, Keith Perkins, and his students, Seong-don Hwang and Dongjin Byun, recently succeeded in a first time ever fabrication of a heterojunction
diode via Chemical Vapor Deposition (CVD) on silicon using synchrotron
radiation. The intense X-ray beam from the SRC Focused White Light beamline
was used to induce the decomposition of a metalorganic molecule, creating a
Boron Carbide/Si(III) junction. Part of this work has been published in: D.
Byun et al., Appl. Phys. Lett. 64, 1968 (1994).
The use of synchrotron radiation to initiate the selective area deposition
of thin film materials from vapor phase chemical precursors has
only recently been explored, with much of the preliminary work being
done at SRC. In a major step forward in the field, Professor Dowbens
research team from the University of Nebraska has shown (see
accompanying figure) that a heterojunction can be fabricated
by this technique. The rectifying behavior of the current versus
voltage curves for a diode grown with the use of synchrotron radiation
assisted decomposition can be seen identified by the solid line,
and the curves for the plasma enhanced CVD grown diodes, the more
conventional fabrication technique, are identified by the broken
This work is an extension of Dowbens past research in direct-write patterning
of boron using synchrotron assisted processing, in combination with unusual
molecular precursor compounds. The importance of the experiment lies in the
potential for combining the high spatial resolution possible with X-ray
lithography, with a process for directly fabricating junctions, and ultimately,
In order to succeed with synchrotron radiation patterning, a suitable molecular
precursor needed to be found, which could be decomposed by the short
wavelengths used in X-ray lithography. After examining the decomposition of
other compounds, Dowben and his colleagues from U. Nebraska and the Naval
Research Laboratory discovered that orthocarborane (C2B10H12) has unique
properties that make it suitable for fabricating semiconductor junctions.
Using Auger spectroscopy, they find that the film composition is close to B5C
following the initiation of film growth. This is similar to the composition
found for diodes fabricated using plasma-enhanced CVD, and the diode
performance using the two methods is similar.
This experiment was part of a project in which Dowben and his group are
studying ways to produce electronics able to withstand harsh environments. The
process they have discovered may have uses in other applications as well. For
example, recent refinements of the method have shown that transistor
fabrication is possible, which is one more step along the quest for
direct-write microelectronic components.
Aladdin -- Editor Brian Tonner email@example.com