@Lior kornblun Thank you for the suggestions.

Are you going to use Ti as back contact on Silicon substrate?

@Anupam Ghosh

No.

If you want the diode faster you have to decrease its junction capacitance and its series resistance since the time constant of the Shottky diode is CjRs. If the barrier height is the same, then the junction capacitance will be the same. Then it remains the series resistance which is mostly controlled by the doping of the semiconductor rather than the metal layer. Here you have to competing effects: the thin oxide which in case of aluminum highly insulating and in case of TiO2 conducting, while the conductivity of aluminum will be higher than that of the titanium. So, one can not judge easily on which metal will be better with higher switching speed.

In addition in case of very thin native oxide layers, it will be tunnelable.

In this case Aluminum will be better.

Best wishes

I agree with Dr. Abdelhalim Zekry.

@ Dr.Abdelhalim Zekry

Thanks a lot! Indeed your answer were perfect!

Dear Kalaivanan,

here is my experience with Al and Ti on Silicon. The best tests (in fact the only reliable tests) of these metal electrodes on Si is the Electrical Impedance Spectroscopy (EIS), where both the conductive as well as dielectric parts of the response can be seen already in the raw data:

1. The Ti evaporated contact on higher resistivity n-type Si gives a very reasonable Ohmic contact, with no signs of TiO2 disruptive influence. In fact we have not measured the presence of this oxide (a series leaky capacitor) in our EIS measurements. Please be aware though that when your Si sample is of lower resistance,. the chemical potential (you call it WF and it is also called Fermi level in semiconductor physics) moves towards the bottom of the Si conduction band, passing on the way the Ti chemical potential (-4.4 ev appr.) and the contact therefore becomes of the non-Ohmic, Schottky variety.

2. Al is a bad choice. The degree of oxidation (often difficult to control) is high (both at the Al-Si interface and Al-further metal wire interface) and EIS is often non-reproducible.

3. I do not understand your mentioning of ZnO ? What is the purpose of this layer ? You state that your system is Silicon Schottky diode ?!

4. The resistivity/conductivity of your metal electrode is irrelevant (in the first approximation) if you are interested in the "speed of switching" of the device. That is determined by the properties of the Schottky depletion layer and that depends on the metal electrode chemical potential (more precisely on the difference between the metal and Si chemical potentials) and not on the metal electrical dc conductivity.

5. The "speed of switching" of the power Schottky diodes is usually regulated by introducing high concentration of deep levels (recombination centres) into Silicon depletion layer, but I do not know whether this process step is available to you.

i hope this will help you on the way.

With best regards

Petr

@petr Viscor

Dear Petr Viscor,

Thanks a lot, indeed, switching speed won't be change much with Ti/ZnO schottky junction rather Al/ZnO. The main factors are Cj and Rs.

I really appreciate your valuable time to clarify my doubts!

Thanks a lot.

Kalai.