Determination of the Built-in Electric Field Near Contacts to Polycrystalline CuInSe2 - Probing Local Charge Transport Properties by Photomixing

The built-in electric field in polycrystalline CuInSe2 (CIS) near gold co-planar contacts was quantitatively revealed for the first time by the photomixing technique. A He-Ne laser beam was focused locally on the CIS sample near one of its contact. While both dc dark and photo-currents showed ohmic behavior, the high frequency ac current was non-zero for zero applied dc bias, which reveals abuilt-in electric field of~1000V/cm. The capability of the photomixing technique to probe local charge transport properties is expected to be very useful for, e.g., the quantitative evaluation of the quality of ohmic contacts and the investigation of electric field induced p-n junction formation in CIS and related materials.