Pd gate MOS sensor for hydrogen detection

The performance of Pd gate MOS hydrogen sensor was studied using C–V and G–V characteristics. The device was fabricated on p-type <100> (1–6Ω cm.) silicon with thermal oxide layer of about 100 Å. The C–V and G–V responses of sensor were measured at different frequencies (1 kHz, 10 kHz, and 100 kHz) upon exposure to hydrogen (conc. 1–8%) at room temperature. It was observed that value of zero bias capacitance decreases with increase in frequency as well as hydrogen concentration. The inversion potential (Vinv.) and flat band voltage (VFB) of the device approach higher values as frequency is reduced. Interface trap density (Nit) was also determined corresponding to the peak in the conductance curve, using a bias scan conductance method at fixed frequency. Nit was found to be decreasing with increasing concentrations of hydrogen. The sensor showed better sensitivity at lower frequency.

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