Dual-band UV/IR optical sensors for fire and flame detection and target recognition

Several military and industrial applications require simultaneous or at least spatially synchronized detection of optical emissions in different spectral regions. The ability to grow III nitrides on Si wafers is considered to be key to the development of multi-color detectors ranging from the UV to IR wavelengths. GaN/InGaN p-n heterostructures grown on Si wafers indicated sensitivity in a wide spectral range from near UV to near IR. Employment of Schottky barrier photodiode structures based on AlGaN alloys allows extension of the spectral sensitivity further into the UV range beneficial for solar-blind sensing. An alternative way to combine sensitivities in separated IR (provided by silicon) and UV (featured by III nitrides) bands by employment of commercially available silicon-on sapphire (SOS) wafers is discussed.