Abstract
Hydrogen sulfide is colorless, flammable and highly toxic gas with typical rotten egg smell. Hydrogen sulfide often results from the bacterial breakdown of organic matters. Because of its toxicity, many hydrogen sulfide personal safety gas detectors are set to alarm at 10 ppm. Most of hydrogen sulfide sensors are made of metal oxide, especially CuO and SnO, and work from room temperature to several hundred Celsius degree. The sensing limit can vary from 10 ppb to 100 ppm. A number of Schottky diodes have been fabricated as gas sensors with catalytic metals since 1980s. Although there are many researches studying in the hydrogen sensing characteristics using Schottky diode, there are still no paper investigating hydrogen sulfide sensing. According to previous researches, Pt/GaN Schottky diode is sensitive to hydrogen and ammonia. Because of its sensing mechanism, it can also be sensitive to hydrogen sulfide. The Ga-face GaN was grown on sapphire substrate by a metal-organic chemical vapor deposition (MOCVD) system. The main structure on the substrate is a Schottky contact, which is formed by Pt and GaN and separated from an Ohmic contact. With present Pt/GaN Schottky diode, we can detect hydrogen sulfide down to 50ppb and get a calibration curve in different concentration. Additionally, this device shows fast response time of around 10 seconds when the concentration of hydrogen sulfide is higher than 1 ppm.