L-Cysteine Functionalized Al0.18Ga0.82N/GaN High Electron Mobility Transistor Sensor for Copper Ion Detection

We demonstrate an Al
_0.18
Ga
_0.82
N/GaN high electron mobility transistor (HEMT)-based copper ion (Cu
²⁺
) sensor with L-cysteine functionalization. The sensing response of the sensor was analyzed by measuring the change in drain current of the HEMT after employing Cu
²⁺
ions of different concentrations in the range of 0–20 mg/L forming complexes with L-cysteine. The Al
_0.18
Ga
_0.82
N/GaN HEMT sensor exhibits high response with a sensitivity of
$82.22~\mu \text{A}$
/(mg/L) and a detection limit of 0.01 mg/L. As a result, the Al
_0.18
Ga
_0.82
N/GaN HEMT sensor functionalized with L-cysteine provides a promising approach for efficient, fast, and convenient detection of Cu
²⁺
.