Operation of guard rings on the ohmic side of n+–p–p+ diodes

Detectors from high-resistivity p-type silicon with multi guard rings structure located on the ohmic side have been investigated. The processed detectors were constructed with four p+-rings surrounding the central p+-pad. The n+–p junction opposite to the contact with rings had not any protection and was cut-through by chip scribing. Investigation of the potential distribution between the floating p+-rings has shown that the potential difference arises just after the depletion of the detector bulk and is accompanied by the detector leakage current saturation. The saturated current is mainly a leakage current flowing in a scribed periphery. Grounding of one of the p+-rings to collect the detector leakage current allows the separation of the bulk and the surface components of the current, which reduces the current of a central p+-pad contact down to tens nA/cm2. A model based on the field effect in the gap between the neighboring p+-rings is proposed. The experiments carried out in this study show that construction of the ohmic side of Si detectors with multi guard rings is a perspective approach to design the detectors operational at high biases. Detectors processed in this way allow one to apply biases up to 600 V.