tesi R. Miscioscia.pdf - EleA@UniSA

Gate-leakages 89
The results are:
= 35.4 nm Polyimide
= 35.1 nm Polystyrene
= 37.8 nm Resist
These data do not show relevant differences in the films structure.
3.3.2 Electrical characterization and device modeling
figure 6 shows that the output characteristics for the PI sample,
before the annealing process, fail zero-crossing at VDS = 0 V. This
effect can be attributed to a leaky gate insulator [10]. Moreover, since
the sample revealed a symmetric Drain-Source behaviour, we can
suppose the leakage current to be IS = ID = IG/2 at VDS = 0 V, as stated
in [10].
Plotting IS(VDS = 0 V) vs. VGS (see figure 4), a quadratic trend can
be noticed. This result is common in many dielectric materials with
trap-free Space-Charge Limited Current behaviour (SCLC). Thus the
parasitic currents between the Drain contact and the Gate can be
modeled by IG~VGD 2 obtaining:
eq. 1 = −K
( V −V
)
2
2
[ V −V
] − V
I S 2 GS T DS DS α DG
where α can be named non-ideality factor.