Recently, I measured the activation energy of the heterojunction based diode via temperature dependent I-V measurement using Arrhenius plot. I obtain Ea which increases with increase in forward bias voltage. I expect other way round, Ea should decrease with increase in biasing. Can this be explained or observed before? Any references on this will be helpful?
Dear Gaurav,
welcome,
To measure the activation energy of the diode current you have to measure the current as a function of temperature while plotting Log I versus 1000/T with T in Kelvin. From the slope you can get the apparent activation energy.
For that you have to be sure of the following:
- the effect of the shunt resistance is eliminated, and
- the effect of the series resistance is eliminated
In this case only the junction current versus voltage and T will be observed.
Best wishes
Dear Prof. Zekry,
Thanks for your response to my query. Do you mean that shunt and series resistance could be possibly responsible for increase in activation energy with voltage? Could you also guide how effect of resistances can be eliminated?
Thanks
Regards
Gaurav
Dear Gaurav,
welcome,
The effect of the shunt resistance dominates the diode current at low current value, while the series resistance affect it at high current value. So, please plot logI versus V keeping T constant, you will be able to divide the I-V curve into the three regions: The low current region dominated by the Rsh, the high current region dominated by the Rs and the intermediate region dominated by diode current mechanism. Then investigate the current in this region as a function of temperature you will get the apparent activation energy of diode current affected only the diode current conduction mechanisms.
To see how the log plot can help in distinguishing the different ranges hinted above please see the link: Article A distributed SPICE-model of a solar cell
Best wishes
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