Photoelectrochemical passivated ZnO-based nanorod structured glucose biosensors using gate-recessed AlGaN/GaN ion-sensitive field-effect-transistors

The AlGaN/GaN heterostructure and the ZnO-based nanorod array were utilized to realize the high sensitive ion-sensitive field-effect-transistor (ISFET) glucose biosensors. The photoelectrochemical (PEC) etching method, the PEC oxidation method, and the PEC passivation method were respectively applied in the fabrication process for improving the glucose sensing performances. A better channel controlling ability of the gate-recessed structure could be obtained by using the PEC etching and oxidation methods in the gate-recessed AlGaN/GaN ISFET glucose biosensors. Additionally, the PEC passivated ZnO-based nanorod array could further increase the sensing surface area and suppressed the Fermi level pinning effect induced by the dangling bonds and the surface states resided on the sidewall surface of the ZnO-based nanorods. Therefore, the passivated ZnO-based nanorod/gate-recessed AlGaN/GaN ISFET glucose biosensors exhibited resulting superior sensing performance compared with the other glucose biosensors. A pH sensitivity of 57.66 mV/pH and a glucose sensitivity of 38.9 μA/mM within the glucose concentration range from 800 nM to 25 mM were obtained. Besides, a low apparent Michaelis–Menten constant of 1.91 mM was also obtained.