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

TLDR

The study introduces an impedance analysis method that reliably determines doping concentration and built‑in potential in nonideal semiconductor p‑n diodes with poor shunt/series resistance or saturation current. The method employs the classic 1/C² vs V representation, extracts small‑signal capacitance from the impedance frequency dependence, and determines series and shunt resistance at each reverse bias. The technique was validated on high‑quality silicon wafer diodes and demonstrated on polycrystalline silicon thin‑film diodes on glass substrates.

Abstract

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.