Development of polycrystal GaAs solar cells. Quarterly technical progress report No. 2 for May 1-July 31, 1979 Page: 68 of 77
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This technique has great potential in grain boundary studies and
much related fundamental work remains to be done. We believe that it may
be possible to resolve the question of whether the properties of grain boun-
daries in GaAs are intrinsic or extrinsic, a question that has an important
bearing on efforts to modify grain boundary properties. The method is ver-
satile in that different levels can be brought into prominence by adjusting
the method of excitation. The method has a bright future for the study of
grain boundaries, provided its full potential is developed.
5.5 Photo-Induced Transient Spectroscopy
Photo-induced transient spectroscopy (PITS) is a transport tech-
nique which detects the transient rise or decay of the sample photocurrent
during chopped illumination. A typical PITS spectrum is obtained by sampling
either the photo current rise (R-PITS) or decay (D-PITS) at two points in
time, with the difference AI = [I(t1) - I(t2)] recorded continuously as a
function of temperature. Any peaks observed in the spectrum will correspond
to a trap emission rate et which is directly proportional to the sampling
rate At- = (t2 - t )-I. Successive temperature scans at different sampling
rates can therefore determine both the trap energy and capture cross section,
assuming a single-exponential rise or decay.
The detection of traps at grain boundaries can be accomplished
by the use of ohmic surface contacts in the use of semi-insulating substrate
material, or a semi-transparent Schottky barrier over the grain boundary in57
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Miller, D. L.; Cohen, M. J.; Harris, Jr., J. S.; Ballantyne, J.; Hoyte, A. & Stefanakos, E. Development of polycrystal GaAs solar cells. Quarterly technical progress report No. 2 for May 1-July 31, 1979, report, September 1, 1979; Golden, Colorado. (https://digital.library.unt.edu/ark:/67531/metadc1057137/m1/68/: accessed April 18, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.