Hi,
The series resistance of the Schottky contact is of the order kilo-ohm. An order of current change has occurred when the voltage is increased to 1.5 V. Are there any applications of such contacts or is that simply mean the contact has not properly established?
Dear Indudhar,
As i understood from your data that your device is a front surface Aluminum- moderately doped n -silicon- Aluminum and the area of the aluminum is 0.4cm^2.
If this is the case then you have as Dreher hinted in his first comment after displaying your I-V curve , metal-Si-metal structure. If the the two metal- si contacts behave similar as Schottky dioes then one of them will be forward biased and the other will be reverse biased. The reverse biased one will be the cause of the high ohmic behavior. You can check this hypothesis by measuring the reverse direction till the device conducts current s as in the forward direction. If this is the case, you will get a similar I-V shape as in the forward characteristics. In order to have a schottky diode, one the contacts must be rectifying and the other must be ohmic with low resistance as per my first comment. As the area increases the current increases for the same applied voltage and the device resistance gets smaller.
Another doubt is that you have to anneal your contacts at relatively high temperature to have a good contact between the metal and silicon. For ohmic contacts one has to anneal the metal aluminum at about 450 degree centigrade under nitrogen ambient.
wish you success
The Metal- Semiconductor contacts can either behave Ohmic or rectifying. In case of rectifying it is termed shottky diode. You did not tell us what type of M-S contact you have. However, in both cases, it is required that the contact has as low resistance as possible. The concept is that if the M-S contact serves as a metal electrode of a bulk device, then the voltage drop on the contact must be much smaller than that on the device bulk. In case the MS contact works as a rectifying diode, the voltage drop on the junction must be dominating the the other voltage drops which means that the drop in the series resistance must be much smaller than the voltage on the junction.
It seems that is not the case with your contacts. So, you have to make more efforts to reduce the series resistance to conform with the above criteria.
wish you success
Adding my 'litle bit'...
You did not give a curve plot and it would be interesting to see an I/V curve with negative as well as positive voltages.
But interpreting your bit of data I'm not sure that you've got a reasonable diode at all. some 1.5 V forward voltage would even be much for an Si diode. What's the substrate you are working with?
Regards
Did you try to measure the AC characteristics? Maybe you can employ the capacitive coupling effects of your high-ohmic contacts.
Hi Dreher,
It is Al/Si Schottky diode, attached is the plot.
Could you provide also the units of measurement that are relevant for the chosen axis scaling?
At which locations did you measure the voltage? Did the ohmic resistance of the wiring contribute, or did you employ sense contacts as close as possible to the device under test?
V and A respectively. Sense contacts are used, Ohmic contacts were not prepared for back contacts.
what is the conduction type and doping of your substrate and what is the annealing temperature of the contact?
best wishes
substrate is n-type, doping concentrations is not known but Phosphorus doped (moderately doped), and annealing is not done.
How can you talk about having Schottky contacts at all? Yes, you have a metal (which one, by the way?) and a moderately doped semiconductor, but this does not mean that you have a Schottky contact -- it just means that you might get a Schottky contact. But as long as you do not have ohmic contacts to the other side of the wafer, how do you want to obtain information about the side of interest? You current--voltage characteristic might just be limited by the bad contact at the back.
Another relevant number is missing: What is the (nominal) contact area of your "device"? So, assumnig a (more or less) homogeneous current flow, what current densities did you obtain?
Hi Wagner,
The effective contact contact area was around 0.4 cm2 and I have got one more doubt—should I fabricate the diode with same Schottky and back ohmic contact area or is that not a significant effect? (I guess there might be contribution of additional series contact resistance due to greater ohmic contact area). Thanks for your replies.
Dear Indudhar,
As i understood from your data that your device is a front surface Aluminum- moderately doped n -silicon- Aluminum and the area of the aluminum is 0.4cm^2.
If this is the case then you have as Dreher hinted in his first comment after displaying your I-V curve , metal-Si-metal structure. If the the two metal- si contacts behave similar as Schottky dioes then one of them will be forward biased and the other will be reverse biased. The reverse biased one will be the cause of the high ohmic behavior. You can check this hypothesis by measuring the reverse direction till the device conducts current s as in the forward direction. If this is the case, you will get a similar I-V shape as in the forward characteristics. In order to have a schottky diode, one the contacts must be rectifying and the other must be ohmic with low resistance as per my first comment. As the area increases the current increases for the same applied voltage and the device resistance gets smaller.
Another doubt is that you have to anneal your contacts at relatively high temperature to have a good contact between the metal and silicon. For ohmic contacts one has to anneal the metal aluminum at about 450 degree centigrade under nitrogen ambient.
wish you success
Dear Abdelhalim Zekry,
Thanks for your insights and response.
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