Effects of Ti addition and annealing on high-k Gd2O3 sensing membranes on polycrystalline silicon for extended-gate field-effect transistor applications

Gadolinium oxide (Gd2O3) and gadolinium titanium oxide (Gd2TiO5) sensing membranes were deposited on polysilicon substrates and applied in the extended-gate field-effect transistor (EGFET) for pH detection. Effects of Ti addition and annealing on the sensing films have been investigated by multiple material analyses and electrical characterizations. The sensing performance could be improved with proper post-annealing and Ti addition because of reinforcements of crystalline structures and electrical reliability. Gd2TiO5 sensing membranes annealed at a temperature of 800 °C could achieve high sensitivity, high linearity, low hysteresis voltage, and a low drift ratio, which is promising for future generation of bio-medical device applications.