Measurement and comparison of silicon p-i-n-photodiodes with ac impedance at different voltages

The dark alternating current (ac) parameters of commercially available silicon p-i-n -photodiodes are measured and compared at room temperature both in forward and reverse bias using the impedance spectroscopy technique. The ac behavior of the photodiodes is found to be almost the same. For bias voltages in the range from −0.8 to 0.0 V, the typical photodiode behaves like a pure capacitor. For higher voltages ( V >-0.2 V) the impedance spectra are nearly semicircular and typically distorted on the high frequency side. At 0.2 V the distortion apparently arises from one of the two interfaces. However, at high bias voltages the nature of the distortion is attributed to the variation of photodiode capacitance and resistance with measurement frequency.