1 research outputs found
Negative Photoconductance in Heavily Doped Si Nanowire Field-Effect Transistors
We
report the first observation of negative photoconductance (NPC)
in n- and p-doped Si nanowire field-effect transistors (FETs) and
demonstrate the strong influence of doping concentrations on the nonconventional
optical switching of the devices. Furthermore, we show that the NPC
of Si nanowire FETs is dependent on the wavelength of visible light
due to the phonon-assisted excitation to multiple conduction bands
with different band gap energies that would be a distinct optoelectronic
property of indirect band gap semiconductor. We attribute the main
driving force of NPC in Si nanowire FETs to the photogenerated hot
electrons trapping by dopants ions and interfacial states. Finally,
comparing back- and top-gate modulation, we derive the mechanisms
of the transition between negative and positive photoconductance regimes
in nanowire devices. The transition is decided by the competition
between the light-induced interfacial trapping and the recombination
of mobile carriers, which is dependent on the light intensity and
the doping concentration