p type versus n type

[esp]

i am having a problem getting a proper IV curve for a p type device ... question .. is there any difference in atk if i have left side source p type, and right side drain n type, and i want to put Vsd = 0.5V .. is there any difference between the following code:

calculator(electrode_voltages=(0.0*Volt, -bias)),

or

calculator(electrode_voltages=(bias,0.0*Volt)),


?

It seems to me there should not be any difference but please confirm ..

then for the gate voltage, if i specify the gate as:

device_configuration.setMetallicRegions([metallic_region0(value = useVgs)] )

where is this referenced to?  I assummed it would be to wherever 0V is, or to some hypothetical ground node somewhere ... can you confirm?  IT seems the voltage you supply here is absolute correct, referenced to some 0V ground node assummed by the system?

[esp]

i think i solved my problem, not taking into account the Dirac point shift for GNR device... i still wonder about the reference for gates though . basically i am hoping it is not somehow automatically referenced to one of the electrodes, instead of 0V ..

[Anders Blom]

Old thread, but I realized a good answer was missing:

The work functions of the source/drain electrodes determine the zero point of the gate bias. That is, if the electrodes have w=4 eV and the gate has w=5 eV then if you set a gate voltage 0 V, it really corresponds to an experimental gate bias of -1 V.