Photoresponses in In2O3transparent gate MOS capacitors

In this paper electrical and photoelectronic properties of sputtered In
2
O
3
films including 5 wt % SnO
2
and transparent gate MOS capacitors employing this film were discussed. In order to improve the characteristics of the sputtered films and to recover the radiation damage generated during the sputtering process, high-temperature annealing of the film in nitrogen was important. In the present experiment, the best post-annealing temperature was about 850°C, and the minimum resistivity ρ and the interface-state density N
ss
which resulted from this annealing were 1.1 × 10
^-3
Ω . cm and 6.5 × 10
¹⁰
cm
^-2
. eV
^-1
, respectively. The dark current was comparable to that of conventional Al-gate MOS capacitors. Moreover, it became clear that the recombination loss of photogenerated carriers due to the interface states caused the degradation of the spectral response in the short wavelength range, when the surface of the MOS substrate was maintained in the vicinity of mid-gap potential. However, the transparent gate MOS capacitors biased in weak or strong inversion could be usable as high-sensitivity, photosensors in the blue region of the spectrum, because the interface states could not act as effective recombination centers for these bias conditions.