Detection of Cl- Ions with AlGaN/GaN High Electron Mobility Transistors

Abstract

AlGaN/GaN high electron mobility transistors (HEMTs) with Ag/AgCl gate are found to exhibit significant changes in channel conductance upon exposing the gate region to various concentrations of chorine ion solutions. Ag/AgCl gate electrode, prepared by potentiostatic anodization, changes the electrical potential when encounters chorine ions. This gate potential changes lead to a change of surface charge in the gate region on the HEMT, induced a higher positive charge on the AlGaN surface, and finally increases the pizeo-induced charge density in the HEMT channel. These anions create an image positive charge on the Ag gate metal for the required neutrality, thus increase the drain current of the HEMT. The HEMT source-drain current showed a clear dependence on the chorine concentration. The limit of detection (LOD) achieved was 1×10-8 M using a 20µm × 50µm gate sensing area.