Analysis of Current Drift in Al2O3 Gated Junctionless pH Sensitive Field Effect Transistor

In this paper, the non-ideal effect, i.e., drain current drift phenomena, has been studied for the first time in the fabricated junctionless ion-sensitive field-effect transistor (JLISFET). The transient analysis has been performed for the measurement of the drain current drift for different pH solutions and gate-bias $(V_{lg})$. The investigations show that hydroxyl ions $OH^{-}$ are responsible for the modification of $Al_{2}O_{3}$ sensing film, which is further responsible for the drain current drift in the JL-ISFET device. A maximum drain current drift of 75.2% and 79.3% have been measured for pH = 9 and $(V_{lg}) = -2V$, respectively. The results verify that the hydroxyl ions play an important role in drain current drift. Furthermore, the effect of channel length lch on drain current and pH sensitivity has also been investigated, and it has been observed that the drain current decreases with the increase in channel length and pH sensitivity is in directly proportional relationship with the lch. The maximum pH sensitivity of 58.2 mV/pH was obtained for a channel length of $25 \mu m$.