While measuring the stress bias effect on designed OFET, I found that the drain current is increasing than current at ZERO time. This increment is more than 30 % of current at ZERO time. I have gone through several literatures, but I am not getting real phenomena. The OFET made with high k dielectric material as gate dielectric.
Hi sir, thank you for your kind response. The anomalous behavior starts from 1 sec onwards. Initially, I have applied constant bias voltage between source and drain. Then, the gate bias have been given. At drain, the out-put current was measured with respect to time. As you said, if it is joule heating, it have to appear after long time bias, but in my case, it starts from initial step onwards. Please have a look on the attachment.
The shift of the threshold voltage, that induces the current increase, is probably due to the gate dielectric, indeed silicon dioxide devices show different behaviour. This effect is quite typical for devices with polar gate dielectrics. Self heating of the device can also occur when high drain voltage is applied (high drain current) and the devices are fabricated on insulating substrate. For a review on the instability mechanism in OTFT see (for instance) Sirringhaus, Advanced Materials 2009, p.3859.
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