Group III-Nitride Chemical Nanosensors with Optical Readout

In order to fully profit from the increased sensitivity of nanoscale transducer structures appropriate readout techniques are required. In this context optical methods are highly promising as they allow parallel probing of large ensembles of nano-objects without manipulating or processing single nanostructures. Furthermore, optical readout techniques feature significant advantages for certain applications as, e.g., measurements in potentially hazardous environments that prohibit any form of electricity at the point of measurement. In this article we discuss a novel type of gas-sensitive nanophotonic probes that are based on the photoluminescence response of group III-nitride nanostructures. This material class offers manifold possibilities for the synthesis of nano-objects as well as for the realization of complex semiconductor heterostructures. The latter is inevitable to fully exploit this optical approach by utilizing band engineering methods for a targeted control of the emission properties (such as the absorption behavior, the emission wavelength and intensity, as well as the temperature stability of the emission). In recent years, significant progress in terms of gas sensing applications has been obtained using GaN/AlN quantum dot systems as well as GaN nanowire ensembles with embedded heterostructures of either GaN/AlGaN or GaN/InGaN. These nanoscale transducer structures are highly suitable for the development of optical sensor systems and proved to be fully competitive to conventional sensor concepts. The state of the art of group III-nitride opto-chemical gas sensors is reviewed in the present chapter.