An accurate characterization of interface-state by deep-level transient spectroscopy for Ge metal-insulator-semiconductor capacitors with SiO2/GeO2 bilayer passivation

Abstract

For Ge metal-insulator-semiconductor (MIS) capacitors with a GeO2 interfacial layer, interface-state density (Dit) was accurately characterized using deep-level transient spectroscopy. Elimination of the influence of slow-traps in the gate dielectric film on Dit characterization is described in detail. This was achieved by optimizing the injection pulse and quiescent reverse-bias voltages at each temperature. Dit values of approximately 5 × 1010 cm−2 eV−1 were observed at around mid-gap for both the n- and p-Ge-MIS capacitors with a TiN-gate, for which an asymmetric U-shape energy distribution in Dit was also observed. Furthermore, the effects of post-metallization annealing (PMA) on Dit improvement and slow-trap passivation were also investigated for Al-gated p-Ge-MIS capacitors, on which the defect passivation mechanism in Al-PMA is discussed. A reasonable correspondence was also observed between gate-film quality for Al-gated p-Ge-MIS capacitors and channel mobility in Ge-p-MIS field effect transistors with the gate fabricated by the same process as for p-Ge-MIS capacitors.