I have fabricated MESFET by depositing GeSe thin film on glass substrate and then deposited silver metal for gate. Now when I record I-V between source and drain at 0 gate voltage it passes from origin, but as I increase of decrease the gate voltage then I-V does not pass from origin, instead I get 0 current when the voltage between source and drain reaches the value of gate voltage. i.e. if I apply gate voltage of 5V then the current value is 0 at drain voltage 5V, if gate voltage is -5V then the current value is 0 at drain voltage -5V.
Can anyone suggest the reason for such behaviour or any literature explaining such behaviour.
Thank you in anticipation.
Regards,
Chaitanya.
It seems that the source voltage is coupled to the gate one. How did you isolate the source from the gate ?
Giuseppe Curro well I have first deposited a thin film of GeSe on a glass slide and then on that I deposited Silver thin film. Two contacts from GeSe were taken from either side of Silver film and one contact was taken from Silver film but from the region where there is no overlapping of GeSe and Silver. Please find the schematic diagram of the device in the attached image.
You said that applyng -5V to the gate your current is zero only when the drain is biased at the same -5V value... GeSe is p-type, hence no current shoud pass at all if the gate voltage is negative (but a small amount at list, however not in a linear fashion). Whatever the gate polarization, is your full charaxterics fet. (diode-) like ? The shape of your IV curves could provide an answer to your question, I think.
Giuseppe Curro Thank you for your valuable answer. I will get back to you with the IV curves of my device as soon as possible. Although it may take time of few days as we have vacation of 2 weeks here on the occasion of Diwali festival.
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