I would like to mention about a non-optical method which may be of use. It is Four-Probe-Method. Pls google for the procedure.

What do you mean by type of electrical conductivity??

@ k.S. Mahesh

Thank you Mr. Mahesh for your suggestion.But i need to use my absorption or Reflectance spectrum to find whthr my material is a p or n type SC.

@ Arindam Malick

whther its a p or n-type material..

There is very simply experimental method: you should modulate(sine voltage, low frequency – about 1 kHz) incident on the semiconductor sample laser beam by an electrooptical modulator. Then you should observe at the oscilloscope (2-chanel) two signal – one from generator which supply modulator and second from the sample (you should apply electrodes on the face of sample and, if necessary, (low photoconductivity of sample) you should bias to the sample a direct voltage – several volts. Because current from generator is electron current in case of electron conductivity of sample you will see in-phase signals from generator and sample, in case of hole conductivity of the sample you will see antiphase signals. Energy of photons should overlap a semiconductor energy gap (band gap). Otherwise there is generation of photo-induced charge carriers from extrinsic levels in the band gap and they could be minority carriers (unnecessarily).

A common method to determine whether your material is p- or n-type is the Hall measurement. You can combine it with a 4-point probe measurement by using the van der Pauw geometry. By that you circumvent the need for optical components (but 'pay' with the need for a magnetic field...)

Some work was done looking at reflection difference spectroscopy (or reflection anisotropy spectroscopy) looking at changes in III-V semiconductors near the E1 transitions due to the inverse electro-optic effect. The technique is simple, but needs to be calibrated to the sample (or using a detailed calculation).

@ Todd Holden

Thank you for your answer.

Can you please suggest a source to refer the work u mentioned??

All suggestions are intereseting: Hall measurements and PhotoLuminescence will directly tell you wheter is n-type or p-type, though metal oxides do not behave as good as semiconductors do, so you may have an unambiguous result. Directly from absorptance and reflectance measurements you can estimate the optical band-gap by Tauc method, but it does not tell you the carrier nature. Which oxide are your working with? Normally, as suggested, the type of defect will indicate you (if it is an Oxygen or metal vacancy).

@ Guillermo Domínguez-Cañizares

Currently am working with CuO ( Cupric oxide) .

(I've re-though my prior comment on Photoluminiscence: not sure if this technique will tell you the type of carrier (n or p) but it probably will work with DLTS...

To determine the conductivity type of a semiconductor by optical means one can use surface photovoltage (SPV) spectroscopy [you might want to see our paper: V. Donchev, K. Kirilov, Ts. Ivanov, K. Germanova

”Surface photovoltage phase spectroscopy– a handy tool for characterisation of bulk semiconductors and nanostructures”, Mat. Sci. & Engineering B: Solid State Materials for Advanced Technology 129 (1-3) 186-192 (2006) ]. the phase of the SPV signal is related to the direction of the band bending at the surface. the latter is usually upward for n-type and downward for p-type.

The use of photoconductivity would’t help because the light (with energy above bandgap) generates both electrons and holes and in an external field both electrons and holes contribute to photocurrent with the same direction.

I agree with Dr. Donchev. We have had much success with the SPV technique in determining conductivity types of metal oxides optically.