Optimal Bias Conditions for FET-type Gas Sensors to Minimize Current Fluctuations

In this work, we introduce a method to improve gas detection characteristics of FET-type gas sensors by using optimal operation bias conditions while maintaining the same sensing material. When a sensing material chemisorbs the gas, effective charges are formed on the sensing material. These charges induce a potential change, transmitting this change to the Si channel. The current change due to gas reaction and current fluctuations both affect gas detection. The gas reaction causes a change in the threshold voltage of the sensor and causes different current fluctuations depending on the operating region. The smaller the current fluctuation, the more accurately the sensor can detect the gas. It is observed that the larger the V
CG
and the smaller the V
DS
, the smaller the current fluctuation. By operating the sensor in the linear region (V
CG
= V
th
+ 1.2 V, V
DS
= 0.1 V) rather than the subthreshold region (V
CG
= Vth- 0.3 V, V
DS
= 0.1 V), the standard deviation of the Gaussian distribution of the current fluctuation can be reduced by ~100 times.