Deep depletion phenomenon of SrTiO3 gate dielectric capacitor

Abstract

SrTiO 3 (STO) thin films were deposited on p-type silicon substrate by radio-frequency (rf) magnetron sputtering in an Ar–O2 and Ar–N2 mixed ambient to form metal/insulator/semiconductor (MIS) structure. We found the Schottky emission and Fowler–Nordheim tunneling mechanisms as responsible for the leakage current in the STO-based MIS structures at low and high electric fields under negative bias voltage, respectively. On the other hand, it was also observed that the generation current dominated the leakage mechanism at the high electric field under positive bias voltage due to the highly leaky insulator and lack of electrons. To maintain the leakage current at the higher electric field, the depletion width would broaden to generate more electrons, which is called deep depletion. Therefore, deep depletion was induced by high leakage current density under positive bias voltage. We also investigated the correlation between deep depletion and the leakage mechanism in STO-based gate dielectric capacitors under positive bias voltage to extract the generation lifetime of silicon substrates. The extracted generation lifetime can be used to examine the quality of silicon substrates after different processing conditions.