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Explicit Gain Equations for Single Crystalline Photoconductors
journal contribution
posted on 2020-03-04, 21:03 authored by Jiajing He, Kaixiang Chen, Chulin Huang, Xiaoming Wang, Yongning He, Yaping DanPhotoconductors
based on semiconducting thin films, nanowires,
and two-dimensional atomic layers have been extensively investigated
in the past decades. However, there is no explicit photogain equation
that allows for fitting and designing photoresponses of these devices. In this work, we managed to derive explicit photogain equations for
silicon nanowire photoconductors based on experimental observations.
The silicon nanowires were fabricated by patterning the device layer
of silicon-on-insulator wafers by standard lithography that were doped
with boron at a concentration of ∼8.6 × 1017 cm–3. It was found that the as-fabricated silicon
nanowires have a surface depletion region ∼32 nm wide. This
depletion region protects charge carriers in the channel from surface
scatterings, resulting in the independence of charge carrier mobilities
on nanowire size. Under light illumination, the depletion region logarithmically
narrows down, and the nanowire channel widens accordingly. Photo Hall
effect measurements show that the nanowire photoconductance is not
contributed by the increase of carrier concentrations but by the widening
of the nanowire channel. As a result, a nanowire photoconductor can
be modeled as a resistor in connection with floating Schottky junctions
near the nanowire surfaces. Based on the photoresponses of a Schottky
junction, we derived explicit photogain equations for nanowire photoconductors
that are a function of light intensity and device physical parameters.
The gain equations fit well with the experimental data, from which
we extracted the minority carrier lifetimes as tens of nanoseconds,
consistent with the minority carrier lifetime in nanowires reported
in literature.
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photogain equationsphoto Hall effect measurements showdepletion region logarithmicallycharge carrier mobilitiesminority carrier lifetimeExplicit Gain Equationsminority carrier lifetimessilicon nanowire photoconductorsas-fabricated silicon nanowiresnanowire channelSingle Crystalline Photoconductors Photoconductors
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