Hello, im am currently trying to identify possible current conduction mechanisms for graphene schottky diodes by looking at I-V characteristiscs. From reading book "Physics of semiconductor devices" by Sze I know that depending on the strength of applied electric field, electron drift current is expressed by different equations (for mobility regime, velocity saturation regime and ballistic regime J~V^2, J~V and J~V^1.5 respectively). However, double log plotting I-V characteristics gives lines for all of mentioned mechanisms. Is there any experimental or analytical way to distinguish one from another?
Dear Paulius,
welcome,
I would like to pay your attention to look at the the possible conduction Americanism in your structure. The first question is what is the structure of your Schottky diode and if this structure is rectifying or not?
The second important advise is that space charge limited current occurs only in insulating or semi insulating materials with very low mobility such as transport in vacuum or in organic semiconductors.
So, the observed different I-V relationships may be due to nonideal Schottky junction.
This is my opinion for your results.
Best wishes
Dear prof. Abdelhalim,
First of all thank You for taking time to answer my question.
Currently I am looking at all possible mechanisms, because I am not sure whether our diode graphene-silicon junction has natural oxide layer in between graphene and silicon which left over after PECVD deposition of graphene. It may certainly be the case that my Schottky diodes have significant thickness of silicon oxide and therefore its I~V characteristics are different from what is expected for such diodes (looks like reverse bias voltage causes higher currents, which may be caused by some form of tunneling or perhaps space-charge limited current in the layer of SiO2).
What is the type and dopant concentration of Si substrate used?
How did you bias the junction (+ve to graphene & -ve to Si or the opposite)
You would expect that the current transitions from a linear I-V behaviour at low voltage to some higher order I-V behaviour at higher voltage. Check the wiki page on SCLC. There's some pretty basic explanations there. I can also recommend papers for you to read if you want to get a deeper understanding about the theory.
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