Time Dependence of the Capacitance of a MOS Silicon Tunnel Diode under the Influence of Hydrogen

Abstract

The results of theoretical and experimental investigations into the time dependence of the capacitance of MOS silicon diodes with a thin tunnel dielectric and a palladium field electrode under the influence of a gas hydrogen-containing mixture are presented. Analytical expressions are derived that describe the time dependence of the capacitance of the space charge region (SCR) of the MOS tunnel diode operating in depletion and enrichment regimes. It is demonstrated that the time dependence of the SCR capacitance of the MOS diode placed in the gas mixture is caused by diffusion of hydrogen atoms from the field electrode to the SiO _x –n-Si interface. The relaxation time of hydrogen atom accumulation at the interface is 47 s for the diode with a SiO _x layer thickness of ∼3.7 nm placed in the gas mixture with 0.3 vol.% of H₂. It has been established that the flat band voltage and the SCR capacitance of the MOS diode change under the influence of the gas mixture due to the decreased density of surface acceptor states at the SiO _x –n-Si interface, the increased positive charge density in the dielectric, and the decreased contact potential difference.