Resistivity vs T for semiconductors is given in many textbooks, e.g. Sze, Physics of Semiconductor Devices. At high T, sheet resistance decreases further as the intrinsic carrier concentration begins to approach and then exceed the doping level.

You could find some measurements data about the mobility in the silicon in this link

http://www.ioffe.ru/SVA/NSM/Semicond/Si/electric.html

Thanks for the reply. Actually I found at higher temp (550 K) it increases again so wondering what is the reason..

Do you have a figure of these measurements data showing this increase ?

Ok so since resisitivity depends on carrier concentration and mobility there are mixed effects. Mobility decreases with T, so under moderate heating resistivity increases. Once you heat enough that the intrinsic carrier concentration exceeds your doping level, it will probably fall again. Try the calculator at

http://www.pvlighthouse.com.au/calculators/Resistivity%20calculator/Resistivity%20calculator.aspx

I am completely agree with Mr. Schnabel but not with the second part of his answer. Resistivity depends on both mobility and resistivity. So, may be after a particular temperature mobility factor dominating the resisitivity and with increasing temperature you are getting the mobility decreased as well as conductivity.

In my humble opinion we have to take in accound that different mobility dependence on temperature. It is T power (3/2)a t low temperatures and T power (-3/2) at high temperatures. Looking in my old text books and come back with more detailes

I found on the net this doc. It s not belonging to me. It explains the different regims of temperature depenence of mobility depending on predominant scattering process.

It seems the first half the Rsh decreases with T, which may from dopant ionization with temperature, when it saturates the carrier concentration will "not" change until intrinsic carrier dominates, then the Rsh change will be determined by carrier mobility which decrease with temperature and Rsh increase with T. You can confirm this by comparing the same measurement with c-si with different doping level to see if the transition temperature increase a little bit with a higher doping level. At very high temperature, then intrinsic carrier dominates, you will see Rsh decrease with temperature.

Dear Sandip Roy,

Did you measure the sheet resistance in vacum or air? If the measurments were carried out in air the inecrease of the sheet resistance may result from the surface oxidation.

Sorry for late reply.. I was out of city. Thanks everyone for the reply...

It was a two probe TLM measurement. The Ohmic contact was nickel silicide. and the measurement was carried in air (cascade).

two probe is not the best means. You must be sure that other parasitic effects are avoided, first of all contact resistance and tip resistance itself. Four-probe is much more secure from that viewpoint. as a matter of facts, interpreting the measurement you have shown may be misleading. If you have a Van der Paw test pattern, or a simply linear 4-pad test structure on your sample, just try again using two (external) forcing tips and two (internal) sensing tips.