Room-Temperature Hydrogen- and Ammonia Gas-Sensing Characteristics of a GaN-Based Schottky Diode Synthesized With a Hybrid Surface Structure

A GaN-based Schottky diode synthesized with a hybrid surface structure is used to fabricate a new room-temperature (25 °C) hydrogen and ammonia gas sensor. This hybrid surface structure includes platinum (Pt) nanoparticle (NP)/SiO2 nanosphere (NS) mixtures and a Pt thin film. The employed hybrid surface structure can effectively increase the catalytic reactivity of the Pt metal and enhance the related gas-sensing characteristics. In the experiment, a higher sensing response of $7.3\times 10^{{5}}$ ( $2.1\times 10^{{1}}{)}$ is obtained under 1% H2/air (1000 ppm NH3/air) gas at 25 °C. Moreover, extremely low detecting levels of 100 ppb H2/air and 100 ppb NH3/air are acquired at 25 °C. The related hydrogen- and ammonia-sensing mechanisms are elucidated in this work. For wireless transmission and Internet of Things (IoT) application, the Kalman filter and shape-preserving piecewise cubic interpolation (SPPCI) algorithms are employed to substantially reduce redundant data and restore original results. More than 86.7% (97%) of the original data points are removed with a small mean recovery error (MRE) of 3% (0.3%) under 1% H2/air (1000 ppm NH3/air) gas at 25 °C.