Impedance analysis: A powerful method for the determination of the doping concentration and built-in potential of nonideal semiconductor p-n diodes

An impedance analysis method is introduced that enables the reliable determination of the doping concentration and the built-in potential of nonideal semiconductor p-n diodes featuring poor values for the shunt resistance, the series resistance, and∕or the diode saturation current. The sample doping concentration on the lightly doped side of the p-n junction and the built-in potential are determined using the classic 1∕C2 vs V representation. The small-signal capacitance C for each reverse bias voltage V is directly extracted from the measured frequency dependence of the sample’s impedance Z. A crucial feature of the method is the determination of the diode’s series resistance and shunt resistance for each reverse bias voltage used. The method is verified using high-quality p-n junction diodes fabricated in silicon wafer substrates and its capabilities are demonstrated on nonideal p-n junction diodes fabricated in polycrystalline silicon thin films on glass substrates.