% is explosive. For this reason, it has become very important to develop highly sensitive hydrogen Ruxolitinib clinical detectors with a large variety of specifications to prevent accidents due to hydrogen leakage. Such detectors should allow continuous monitoring of the concentration of gases in the environment in a quantitative and selective way. Therefore, hydrogen sensors would form an integral Inhibitors,Modulators,Libraries part of any such systems incorporating hydrogen.Solid-state hydrogen sensors under flow-through conditions are mainly classified into the following categories: pyroelectric, piezoelectric, fiber optic, electrochemical, and semiconductor sensors [1]. Among them, semiconductor device hydrogen detectors exhibit the highest sensitivity at elevated temperatures [1].

In many applications such as fuel cells and chemical process monitoring in industries, Inhibitors,Modulators,Libraries gas sensing with high sensitivity and low detection limit in harsh environments is required. Wide-band-gap compound semiconductor materials including Inhibitors,Modulators,Libraries SiC and GaN have been candidates for high-temperature gas sensing applications [2�C5]. Due to the large band-gap of GaN and SiC, and the associated chemical stability and mechanical robustness, these semiconductors can be used for many harsh applications, satisfying a considerable interest in developing hydrogen gas sensors capable of operation in harsh environmental conditions such as high-temperature and chemically corrosive ambients. These include gas sensing operations during chemical reactor processing, onboard fire alarms on aircraft and space vehicles, as well as detection of fuel leaks in automobiles and aircraft, to name but a few.

A unique advantage of a GaN gas sensor is that it can be integrated with GaN-based optical devices or high-power, high-temparature electronic devices on the same chip. Another advantage of nitride-based Inhibitors,Modulators,Libraries semiconductor devices is a utilization of AlGaN/GaN heterostructure. In an AlGaN/GaN heterostructure, the polarization-induced two dimensional electron gas (2DEG) concentration at the AlGaN/GaN interface is extremely sensitive to surface states. Any potential changes on the surface by adsorption of gas or liquid polar molecules, or pressure change would affect the surface potential and modulate the 2DEG density. Therefore, devices on AlGaN/GaN heterostructures have great potential for chemical gas sensing in harsh environments.

Furthermore, the fabrication of nitride-based sensors on Si contributes to lower production cost. On the other hand, technical drawbacks for SiC devices are that the processing, particularly of SiC FETs (field-effect transistors), is inherently Anacetrapib complicated, requiring high-temperature implantation and very high-temperature post-implantation annealing steps, leading Tofacitinib JAK3 to higher cost. Therefore, nitride-based semiconductor sensors are investigated in this report.