A p-i-n UV photodiode is fabricated. The schematic diagram and I-V characteristics is attached with this mail.
1) I would like to know how to convert the current (mA) in terms of current density (mA/cm2) for the calculation of photoresponsivity.
2) What I understood is the area of deposited electrode under which electron holes recombination takes place is considered as active area of the semiconductor device such as (LEDs and Photodiodes) and not the entire thin film surface area. (Please correct me if I am wrong)
2) In the attached device structure, the Au electrode deposited upon the n-ZnO is 1mm diameter. So the radius of the circular electrode 'r' is 0.5 mm and to calculate the current density I have to divide the current(mA)values by the area of circular silver electrode (3.14 x (0.5mm)2 = 0.00785 cm2) inorder to calculate the current density (mA/cm2)? Whether my calculation is correct?
I will be grateful if you can please provide me your valuable suggestions (with probably some related reference papers)
LED / photo-diode is essentially a p-n junction. The current that flow through the diode covers the entire junction area. To calculate current density, you should divide the observed current by the area of junction in Cm2.
So sir I have to divide the current values with that of area of Ag electrodes deposited on the top of n-ZnO layers. Is it correct? Because the Ag electrodes area covers the entire junction area of p-i-n electrodes. Please clarify sir.
Thanks a lot for your kind reply.
The area of overlapping region. If you are using patterned TCO, using masks for thin films and finally Ag electrode. Measure the area where you see ALL in common (minimum). Usually TCO and films have much larger area. Electrode may be little more than the active area but the area you need for current density calculation is the minimum intersected area of the electrodes and the films.
Let me know if you are not getting, I will send you a sketch.
Simply divide the current values with the area of junction. Do not worry about the area of electrode. It may or may not be equal to the junction area. Once again I emphasize that it is the junction area that is to be used for calculating the current density irrespective of the area of electrodes.
Dear Irfan Irfan, Thanks a lor for your reply. If you have no problem can you please send me the sketch work to explain.
Thank you so much in advance.
well it is not easy to determine with high accuracy. Because it is impossible to find out real device area, since it may have very complicated geometrical structure. You can roughly estimate it. After you have estimated effective device area then you have to multiply this value with current density values then you will have current values.
To estimate roughly the current density you have to simly divide your current values by the area of the hole junction, i.e. the area of your deposited film. The effect of the contact pads is taken into account by calculating the current spreading. But for the most applications it is not necessary since it would correct the current values obtained by just some fraction of a percent.
I copied and pasted into a detailed viewer, but I still can't see any detail of your structure; in addition I'm guessing that the two curves on the graph are illuminated and dark , in which case we seem to be looking at some kind of hybrid between a Shottky detector and a photoconductor.
Also, you mention both Au (gold) and silver. Is the front electrode gold and the rear one silver? Is the front electrode transparent?
Regardless of the above, some carriers from outside the electrode region will collected - how far away will depend on the nature of the photoresponse.
The safest way to see what is going on (and hence calculate the arial sensitivity of the active regions) is to map the sensitivity by scanning a small spot across the device; in this way the data should be unambiguous.
The area of the junction and current values matter a lot. so divide the current values with the area of junction , you will get the current density by that.
If I cut 4 cm by 4cm Nafion 115 and I coated on 2cm by 2cm. Please how do I calculate current density. Should I consider only the coated area as my area or the whole cut part?
imply divide the current values with the area of junction. Do not worry about the area of electrode. It may or may not be equal to the junction area
The above answer is exactly the same that I had already spoken earlier.
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