Characterization of hydrogenated amorphous silicon by capacitance‐voltage and surface photovoltage measurements using liquid Schottky barriers

Experimental studies have been made on the electrical properties of hydrogenated amorphous silicon (a‐Si:H) using liquid Schottky barriers. We have found that the quasi‐static capacitance‐voltage (C‐V) method can be applied to the a‐Si:H/quinone‐hydroquinone (Q‐HQ) liquid Schottky junction. This method enables us to determine the net density of positive space charge due to ionized traps and impurities in a‐Si:H (Ne), the built‐in potential (Vb), and the width of the surface space‐charge layer (W), of this liquid junction. The barrier height of an undoped a‐Si:H/Q‐HQ junction has been estimated to be more than 1 eV from the value of Vb thus obtained. By C‐V and surface photovoltage (SPV) measurements on the same samples, we have studied the changes in the properties of a‐Si:H with doping and with prolonged illumination. It has been found that phosphorous (P) doping drastically decreases the hole diffusion length measured by the SPV method and increases the value of Ne. Slight boron (B) doping increases the...