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A hybrid structure of platinum nanoparticles (Pt NPs) and a Pt thin film are employed to fabricate a new Pt NP/Pt thin film/GaN-based Schottky diode-type ammonia sensor. Pt NPs are formed by a drop coating and UV illumination approach. The increased surface-area-to-volume ratio and “spillover” effect of Pt NPs are beneficial in ammonia sensing. Due to the synergistic catalytic activity of Pt NPs and Pt thin film, the studied device shows good ammonia sensing properties, including a high sensing response of 522.1 under 1000-ppm NH3/air gas at 473 K and an extremely low detecting level of 0.4-ppm NH3/air. A thermodynamic analysis is employed to study the related ammonia sensing mechanism. Furthermore, a Kalman filter and the related algorithm are introduced to effectively reduce the redundant data without affecting the original sensing results. Based on the good performance and advantages of a relatively simple structure and easy fabrication, the studied device is promising for ammonia sensing and wireless transmission applications. [ABSTRACT FROM AUTHOR]

This paper investigates the degradation of vertically aligned gallium nitride (GaN) nanowire (NW) arrays submitted to gate bias stress and UV light. Based on electrical tests and simulations, we demonstrate the existence of trapping processes that depend on the applied stress voltage ${V}_{\textsf {Gstress}}$ and on the applied light during stress (wavelength, $\lambda $). We demonstrate the following original results: 1) for positive and negative ${V}_{\textsf {Gstress}}$ conditions, no significant variation in dc characteristics is observed when the samples are stressed in dark and 2) when the devices are submitted to negative ${V}_{\textsf {Gstress}}$ and to UV light, a positive variation in threshold voltage (${V}_{\textsf {th}}$) is observed. The positive ${V}_{\textsf {th}}$ shift is ascribed to the transfer and trapping of electrons from the gate metal to the oxide, promoted by UV light. We also evaluated the temperature dependence of the threshold voltage shift under UV light. We demonstrated an increased trapping at higher temperatures, indicating a role of thermionic processes in electron trapping. On the other hand, detrapping from oxide states proceeds through defect-mediated conduction, i.e., is limited by the number of available states. [ABSTRACT FROM AUTHOR]