Liquid–Solid Interface Engineering of Ultrathin and Solution-Processed Indium Oxide-Based Electrolyte-Gated Transistors by Gallium Doping

The need for rapid, noninvasive detection of biosignals has been increasing, and its platform has been requiring high sensitivity, selectivity, and strong chemical resistance for the detection of biomolecules in a physiological environment. Herein, we propose solution-processed, ultrathin, gallium-doped, indium oxide (GIO) semiconductor-based electrolyte-gated transistors (EGTs) and their patchable and real-time healthcare monitoring platforms. GIO EGTs have higher electrical stability than nondoped indium oxide EGTs, and this possibly could be attributed to the reduction of the oxygen deficiency regarding the interface defects between the electrolyte and the surface of the semiconductor. For the hysteresis test, the rate of change in threshold voltage ( V TH ) when returning to the original pH value in the pH loop was compared, and the average reliability of the indium oxide EGT was improved when gallium was doped. Furthermore, the reliability of the GIO-based flexible EGT device showed a low hysteresis voltage change value of 10 mV in the pH loop. The sensitivity of GIO EGTs reached a maximum value of 78 mV/pH, exceeding the Nernst limit of 59 mV/pH. Thus, we were able to fabricate flexible, patchable GIO EGT-based biosensors with a wireless, communication-based electrical acquisition system and visualization of data in real-time monitoring.