Surface Dependence of pH Sensors on AlGaN/GaN Heterostructure

A pH sensor on an AlGaN/GaN heterostructure with different surface conditions was developed and evaluated. The average sensitivity is 49.5, 47.2 and 51.8 mV/pH, respectively, for samples with i-GaN, p-GaN and n-GaN cap layers on the AlGaN surface. The average sensitivity is 52.9, 53.5, 54.1, and 55.2 mV/pH, respectively, for the samples with an AlGaN surface and Al composition of 22%, 24%, 25%, and 35%. The sensitivity of the pH sensor on AlGaN/GaN heterostructure increases if the AlGaN surface is adopted and increases with increasing aluminum composition