Humidity sensor based on Gallium Nitride for real time monitoring applications

Gallium Nitride (GaN) remarkably shows high electron mobility, wide energy band gap, biocompatibility, and chemical stability. Wurtzite structure makes topmost Gallium atoms electropositive, hence high ligand binding ability especially to anions, making it usable as humidity sensor due to water self-ionization phenomenon. In this work, thin-film GaN based humidity sensor is fabricated through pulse modulated DC magnetron sputtering. Interdigitated electrodes (IDEs) with 100 mu m width and spacing were inkjet printed on top of GaN sensing layer to further enhance sensor sensitivity. Impedance, capacitance, and current response were recorded for humidity and bio-sensing applications. The sensor shows approximate linear impedance response between 0 and 100% humidity range, the sensitivity of 8.53 nF/RH% and 79 k ohm /RH% for capacitance and impedance, and fast response (T-res) and recovery (T-rec) time of 3.5 s and 9 s, respectively. The sensor shows little hysteresis of <3.53% with stable and wide variations for accurate measurements. Especially, it demonstrates temperature invariance for thermal stability. Experimental results demonstrate fabricated sensor effectively evaluates plant transpiration cycle through water level monitoring by direct attachment onto leaves without causing any damage as well as freshness level of meat loaf. These properties of the proposed sensor make it a suitable candidate for future electronics providing a low-cost platform for real time monitoring applications.

Automated summary

Gallium Nitride (GaN) based humidity sensor was fabricated using pulse modulated DC magnetron sputtering, with interdigitated electrodes (IDEs) to enhance sensitivity. The sensor exhibited linear impedance response, high sensitivity, and fast response and recovery times, showing little hysteresis and good stability for accurate measurements. Experimental results demonstrated its effectiveness in evaluating plant transpiration cycle and monitoring freshness level of food products, making it a promising candidate for future electronics applications.