Bimodal wireless sensing with dual-channel wide bandgap heterostructure varactors (original) (raw)

Gas sensing with AlGaN/GaN 2DEG channels Gas Sensing with AlGaN/GaN 2DEG Channels

AlGaN/GaN shows great promise as a generic platform for (biochemical l sensing because of its robustness and intrinsic sensitivity to surface charge or dipoles. Here, we employ the two-dimensional electron gas (2DEG) formed at the interface of AlGaN/GaN layers grown on Si substrates for the ultra-sensitive detection of NO x. In the presence of humidity, the interaction of NO x with the naturally adsorbed water layer at the surface changes the surface polarity, thereby instantaneously affecting the 2DEG conductivity. We show that this concept can be used for ultra-low-power continuous air quality monitoring, at room temperature and humidity levels down to 10%. The extremely low current noise level in our structures enables the reproducible detection of variations in the NO x concentration of 1 ppb. Furthermore, we show that these devices can be functionalized with metalloporphyrins resulting in sensitivity to NO and NO 2 concentrations below 50 ppb even in dry conditions.

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