Ultra-Sensitive No2 Detection With Algan/Gan 2deg Channels For Air Quality Monitoring

Low-ppb room temperature NO2 detection is demonstrated for the first time using ultra-thin AlGaN/GaN heterostructures fabricated on silicon substrates. AlGaN/GaN shows great promise as a generic platform for (bio-) chemical sensing because of its robustness and intrinsic sensitivity to surface charges and dipoles. Here, we employ the two-dimensional electron gas (2DEG) formed at the interface of the AlGaN/GaN heterostructure for the monitoring of low-ppb NO2 concentrations in ambient air. We find that in the presence of humidity, the interaction of NO2 with the open gate area reversibly changes 2DEG conductivity. The dynamic range of these structures can be tuned to that of interest for air quality monitoring (0-100 ppb) by precisely back etching the open gate areas. A slope-based detection scheme in combination with periodic heating-induced gas desorption enables continuous air quality (NO2) monitoring.