Hello Manab Kalita ,

If you want to determine the bulk leakage current at a certain applied voltage difference due to your SiO2 layer on top of n-type Si layer, you will need to make a guarded current measurement so that you exclude surface leakage currents, see the attached figure. The top electrodes consist of an outer annular (ring) electrode surrounding (guarding) a circular inner electrode. The annular electrode intercepts the surface currents so that the inner circular electrode only receives (measures) bulk leakage currents.

Regards,

Tom Cuff

Thank you, Mr. Tom Cuff, for your valuable explanation.